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 $64.49   5.513%   $68.0453   $68.05   $68.05   $68.00  
  Purchase #2 $191.53   10.113%   $210.8994   $210.90   $210.90   $210.90  
  Purchase #3 $36.86   9.385%   $40.3193   $40.32   $40.30   $40.30  
  Purchase #4 $127.81   5.469%   $134.7999   $134.80   $134.80   $134.80  
  Purchase #5 $209.71   3.380%   $216.7982   $216.80   $216.80   $216.80  
  Purchase #6 $150.48   6.247%   $159.8805   $159.88   $159.90   $159.90  
  Purchase #7 $189.64   13.462%   $215.1693   $215.17   $215.15   $215.20  
  7 purchase totals = $970.52       $1,045.9119   $1,045.92   $1,045.90   $1,045.90