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 $67.49   6.634%   $71.9673   $71.97   $71.95   $72.00  
  Purchase #2 $61.33   4.818%   $64.2849   $64.28   $64.30   $64.30  
  Purchase #3 $231.98   5.405%   $244.5185   $244.52   $244.50   $244.50  
  Purchase #4 $100.30   6.669%   $106.989   $106.99   $107.00   $107.00  
  Purchase #5 $109.65   6.591%   $116.877   $116.88   $116.90   $116.90  
  Purchase #6 $122.51   8.189%   $132.5423   $132.54   $132.55   $132.50  
  Purchase #7 $18.64   8.739%   $20.2689   $20.27   $20.25   $20.30  
  7 purchase totals = $711.90       $757.4479   $757.45   $757.45   $757.50