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 $68.83   8.407%   $74.6165   $74.62   $74.60   $74.60  
  Purchase #2 $24.33   12.484%   $27.3674   $27.37   $27.35   $27.40  
  Purchase #3 $14.55   4.663%   $15.2285   $15.23   $15.25   $15.20  
  Purchase #4 $65.73   11.194%   $73.0878   $73.09   $73.10   $73.10  
  Purchase #5 $103.69   3.261%   $107.0713   $107.07   $107.05   $107.10  
  Purchase #6 $41.39   13.668%   $47.0472   $47.05   $47.05   $47.00  
  Purchase #7 $25.53   9.503%   $27.9561   $27.96   $27.95   $28.00  
  7 purchase totals = $344.05       $372.3748   $372.39   $372.35   $372.40