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 $214.73   8.293%   $232.5376   $232.54   $232.55   $232.50  
  Purchase #2 $92.96   9.874%   $102.1389   $102.14   $102.15   $102.10  
  Purchase #3 $150.60   8.213%   $162.9688   $162.97   $162.95   $163.00  
  Purchase #4 $34.82   8.589%   $37.8107   $37.81   $37.80   $37.80  
  Purchase #5 $44.55   10.317%   $49.1462   $49.15   $49.15   $49.10  
  Purchase #6 $93.79   7.669%   $100.9828   $100.98   $101.00   $101.00  
  Purchase #7 $240.49   10.438%   $265.5923   $265.59   $265.60   $265.60  
  7 purchase totals = $871.94       $951.1773   $951.18   $951.20   $951.10