Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $215.55   13.188%   $243.9767   $243.98   $244.00   $244.00  
  Purchase #2 $236.31   10.777%   $261.7771   $261.78   $261.80   $261.80  
  Purchase #3 $165.29   13.680%   $187.9017   $187.90   $187.90   $187.90  
  Purchase #4 $141.82   13.206%   $160.5487   $160.55   $160.55   $160.50  
  Purchase #5 $162.28   4.761%   $170.0062   $170.01   $170.00   $170.00  
  Purchase #6 $184.67   12.807%   $208.3207   $208.32   $208.30   $208.30  
  Purchase #7 $218.76   8.220%   $236.7421   $236.74   $236.75   $236.70  
  7 purchase totals = $1,324.68       $1,469.2732   $1,469.28   $1,469.30   $1,469.20