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 $58.39   6.160%   $61.9868   $61.99   $62.00   $62.00  
  Purchase #2 $189.42   11.206%   $210.6464   $210.65   $210.65   $210.60  
  Purchase #3 $221.46   10.221%   $244.0954   $244.10   $244.10   $244.10  
  Purchase #4 $76.70   12.218%   $86.0712   $86.07   $86.05   $86.10  
  Purchase #5 $42.44   8.276%   $45.9523   $45.95   $45.95   $46.00  
  Purchase #6 $144.36   8.833%   $157.1113   $157.11   $157.10   $157.10  
  Purchase #7 $112.35   12.180%   $126.0342   $126.03   $126.05   $126.00  
  7 purchase totals = $845.12       $931.8976   $931.90   $931.90   $931.90