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 $68.95   5.414%   $72.683   $72.68   $72.70   $72.70  
  Purchase #2 $195.41   11.434%   $217.7532   $217.75   $217.75   $217.80  
  Purchase #3 $108.52   11.580%   $121.0866   $121.09   $121.10   $121.10  
  Purchase #4 $126.80   11.565%   $141.4644   $141.46   $141.45   $141.50  
  Purchase #5 $132.37   8.338%   $143.407   $143.41   $143.40   $143.40  
  Purchase #6 $25.69   7.110%   $27.5166   $27.52   $27.50   $27.50  
  Purchase #7 $111.95   13.443%   $126.9994   $127.00   $127.00   $127.00  
  7 purchase totals = $769.69       $850.9102   $850.91   $850.90   $851.00