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 $117.61   7.106%   $125.9674   $125.97   $125.95   $126.00  
  Purchase #2 $82.93   12.663%   $93.4314   $93.43   $93.45   $93.40  
  Purchase #3 $59.99   10.606%   $66.3525   $66.35   $66.35   $66.40  
  Purchase #4 $178.32   7.690%   $192.0328   $192.03   $192.05   $192.00  
  Purchase #5 $169.87   6.807%   $181.4331   $181.43   $181.45   $181.40  
  Purchase #6 $198.95   7.754%   $214.3766   $214.38   $214.40   $214.40  
  Purchase #7 $84.79   11.612%   $94.6358   $94.64   $94.65   $94.60  
  7 purchase totals = $892.46       $968.2296   $968.23   $968.30   $968.20