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 $91.46   5.185%   $96.2022   $96.20   $96.20   $96.20  
  Purchase #2 $173.41   8.423%   $188.0163   $188.02   $188.00   $188.00  
  Purchase #3 $27.74   4.798%   $29.071   $29.07   $29.05   $29.10  
  Purchase #4 $121.48   4.697%   $127.1859   $127.19   $127.20   $127.20  
  Purchase #5 $187.76   10.441%   $207.364   $207.36   $207.35   $207.40  
  Purchase #6 $229.54   11.456%   $255.8361   $255.84   $255.85   $255.80  
  Purchase #7 $43.43   12.224%   $48.7389   $48.74   $48.75   $48.70  
  7 purchase totals = $874.82       $952.4144   $952.42   $952.40   $952.40