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 $60.54   7.394%   $65.0163   $65.02   $65.00   $65.00  
  Purchase #2 $101.43   4.775%   $106.2733   $106.27   $106.25   $106.30  
  Purchase #3 $204.68   6.874%   $218.7497   $218.75   $218.75   $218.70  
  Purchase #4 $44.27   8.663%   $48.1051   $48.11   $48.10   $48.10  
  Purchase #5 $127.35   5.526%   $134.3874   $134.39   $134.40   $134.40  
  Purchase #6 $140.48   4.756%   $147.1612   $147.16   $147.15   $147.20  
  Purchase #7 $133.43   7.179%   $143.0089   $143.01   $143.00   $143.00  
  7 purchase totals = $812.18       $862.7019   $862.71   $862.65   $862.70