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 $59.97   4.840%   $62.8725   $62.87   $62.85   $62.90  
  Purchase #2 $191.94   4.556%   $200.6848   $200.68   $200.70   $200.70  
  Purchase #3 $48.70   9.544%   $53.3479   $53.35   $53.35   $53.30  
  Purchase #4 $210.72   11.237%   $234.3986   $234.40   $234.40   $234.40  
  Purchase #5 $187.96   4.140%   $195.7415   $195.74   $195.75   $195.70  
  Purchase #6 $82.92   13.417%   $94.0454   $94.05   $94.05   $94.00  
  Purchase #7 $245.56   11.429%   $273.6251   $273.63   $273.65   $273.60  
  7 purchase totals = $1,027.77       $1,114.7158   $1,114.72   $1,114.75   $1,114.60