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 $72.65   4.721%   $76.0798   $76.08   $76.10   $76.10  
  Purchase #2 $97.54   13.311%   $110.5235   $110.52   $110.50   $110.50  
  Purchase #3 $68.54   7.485%   $73.6702   $73.67   $73.65   $73.70  
  Purchase #4 $102.34   6.394%   $108.8836   $108.88   $108.90   $108.90  
  Purchase #5 $108.87   9.260%   $118.9514   $118.95   $118.95   $119.00  
  Purchase #6 $214.69   4.630%   $224.6301   $224.63   $224.65   $224.60  
  Purchase #7 $25.63   6.668%   $27.339   $27.34   $27.35   $27.30  
  7 purchase totals = $690.26       $740.0776   $740.07   $740.10   $740.10