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 $89.68   6.464%   $95.4769   $95.48   $95.50   $95.50  
  Purchase #2 $196.37   6.472%   $209.0791   $209.08   $209.10   $209.10  
  Purchase #3 $90.82   11.758%   $101.4986   $101.50   $101.50   $101.50  
  Purchase #4 $138.38   5.695%   $146.2607   $146.26   $146.25   $146.30  
  Purchase #5 $234.54   13.108%   $265.2835   $265.28   $265.30   $265.30  
  Purchase #6 $31.68   4.787%   $33.1965   $33.20   $33.20   $33.20  
  Purchase #7 $68.71   9.241%   $75.0595   $75.06   $75.05   $75.10  
  7 purchase totals = $850.18       $925.8548   $925.86   $925.90   $926.00