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 $48.61   7.368%   $52.1916   $52.19   $52.20   $52.20  
  Purchase #2 $249.95   10.180%   $275.3949   $275.39   $275.40   $275.40  
  Purchase #3 $41.45   12.731%   $46.727   $46.73   $46.75   $46.70  
  Purchase #4 $188.69   8.163%   $204.0928   $204.09   $204.10   $204.10  
  Purchase #5 $178.67   11.642%   $199.4708   $199.47   $199.45   $199.50  
  Purchase #6 $95.65   7.158%   $102.4966   $102.50   $102.50   $102.50  
  Purchase #7 $10.67   10.269%   $11.7657   $11.77   $11.75   $11.80  
  7 purchase totals = $813.69       $892.1394   $892.14   $892.15   $892.20