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 $214.77   10.169%   $236.61   $236.61   $236.60   $236.60  
  Purchase #2 $211.66   3.651%   $219.3877   $219.39   $219.40   $219.40  
  Purchase #3 $240.46   5.229%   $253.0337   $253.03   $253.05   $253.00  
  Purchase #4 $237.78   10.589%   $262.9585   $262.96   $262.95   $263.00  
  Purchase #5 $88.31   8.477%   $95.796   $95.80   $95.80   $95.80  
  Purchase #6 $156.70   6.773%   $167.3133   $167.31   $167.30   $167.30  
  Purchase #7 $150.96   11.334%   $168.0698   $168.07   $168.05   $168.10  
  7 purchase totals = $1,300.64       $1,403.1690   $1,403.17   $1,403.15   $1,403.20