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 $60.64   3.826%   $62.9601   $62.96   $62.95   $63.00  
  Purchase #2 $148.50   10.269%   $163.7495   $163.75   $163.75   $163.70  
  Purchase #3 $74.55   6.391%   $79.3145   $79.31   $79.30   $79.30  
  Purchase #4 $40.82   12.684%   $45.9976   $46.00   $46.00   $46.00  
  Purchase #5 $49.36   8.399%   $53.5057   $53.51   $53.50   $53.50  
  Purchase #6 $167.89   9.260%   $183.4366   $183.44   $183.45   $183.40  
  Purchase #7 $205.36   4.130%   $213.8414   $213.84   $213.85   $213.80  
  7 purchase totals = $747.12       $802.8054   $802.81   $802.80   $802.70