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 $91.51   6.698%   $97.6393   $97.64   $97.65   $97.60  
  Purchase #2 $166.99   9.682%   $183.158   $183.16   $183.15   $183.20  
  Purchase #3 $117.96   6.750%   $125.9223   $125.92   $125.90   $125.90  
  Purchase #4 $89.28   5.163%   $93.8895   $93.89   $93.90   $93.90  
  Purchase #5 $246.76   6.292%   $262.2861   $262.29   $262.30   $262.30  
  Purchase #6 $93.82   4.533%   $98.0729   $98.07   $98.05   $98.10  
  Purchase #7 $95.53   4.818%   $100.1326   $100.13   $100.15   $100.10  
  7 purchase totals = $901.85       $961.1007   $961.10   $961.10   $961.10