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 $87.61   9.614%   $96.0328   $96.03   $96.05   $96.00  
  Purchase #2 $164.97   13.760%   $187.6699   $187.67   $187.65   $187.70  
  Purchase #3 $86.96   3.566%   $90.061   $90.06   $90.05   $90.10  
  Purchase #4 $185.26   5.492%   $195.4345   $195.43   $195.45   $195.40  
  Purchase #5 $148.82   7.251%   $159.6109   $159.61   $159.60   $159.60  
  Purchase #6 $44.75   13.226%   $50.6686   $50.67   $50.65   $50.70  
  Purchase #7 $154.87   7.479%   $166.4527   $166.45   $166.45   $166.50  
  7 purchase totals = $873.24       $945.9304   $945.92   $945.90   $946.00