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 $85.66   11.747%   $95.7225   $95.72   $95.70   $95.70  
  Purchase #2 $35.77   9.522%   $39.176   $39.18   $39.20   $39.20  
  Purchase #3 $84.93   9.687%   $93.1572   $93.16   $93.15   $93.20  
  Purchase #4 $112.91   8.234%   $122.207   $122.21   $122.20   $122.20  
  Purchase #5 $69.60   8.531%   $75.5376   $75.54   $75.55   $75.50  
  Purchase #6 $180.68   8.642%   $196.2944   $196.29   $196.30   $196.30  
  Purchase #7 $244.77   11.279%   $272.3776   $272.38   $272.40   $272.40  
  7 purchase totals = $814.32       $894.4723   $894.48   $894.50   $894.50