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 $56.54   11.283%   $62.9194   $62.92   $62.90   $62.90  
  Purchase #2 $116.49   5.171%   $122.5137   $122.51   $122.50   $122.50  
  Purchase #3 $11.52   10.502%   $12.7298   $12.73   $12.75   $12.70  
  Purchase #4 $182.26   8.222%   $197.2454   $197.25   $197.25   $197.20  
  Purchase #5 $155.30   7.358%   $166.727   $166.73   $166.75   $166.70  
  Purchase #6 $141.71   6.718%   $151.2301   $151.23   $151.25   $151.20  
  Purchase #7 $217.98   6.486%   $232.1182   $232.12   $232.10   $232.10  
  7 purchase totals = $881.80       $945.4836   $945.49   $945.50   $945.30