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 $187.63   7.856%   $202.3702   $202.37   $202.35   $202.40  
  Purchase #2 $108.47   4.138%   $112.9585   $112.96   $112.95   $113.00  
  Purchase #3 $218.78   8.783%   $237.9954   $238.00   $238.00   $238.00  
  Purchase #4 $48.45   9.670%   $53.1351   $53.14   $53.15   $53.10  
  Purchase #5 $148.30   6.609%   $158.1011   $158.10   $158.10   $158.10  
  Purchase #6 $202.53   11.595%   $226.0134   $226.01   $226.00   $226.00  
  Purchase #7 $37.27   13.696%   $42.3745   $42.37   $42.35   $42.40  
  7 purchase totals = $951.43       $1,032.9482   $1,032.95   $1,032.90   $1,033.00