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 $212.69   9.197%   $232.2511   $232.25   $232.25   $232.30  
  Purchase #2 $85.41   7.234%   $91.5886   $91.59   $91.60   $91.60  
  Purchase #3 $12.39   9.252%   $13.5363   $13.54   $13.55   $13.50  
  Purchase #4 $21.87   7.182%   $23.4407   $23.44   $23.45   $23.40  
  Purchase #5 $57.40   4.763%   $60.134   $60.13   $60.15   $60.10  
  Purchase #6 $185.27   7.577%   $199.3079   $199.31   $199.30   $199.30  
  Purchase #7 $218.79   11.144%   $243.172   $243.17   $243.15   $243.20  
  7 purchase totals = $793.82       $863.4306   $863.43   $863.45   $863.40