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 $181.60   7.786%   $195.7394   $195.74   $195.75   $195.70  
  Purchase #2 $34.57   3.123%   $35.6496   $35.65   $35.65   $35.60  
  Purchase #3 $164.68   8.116%   $178.0454   $178.05   $178.05   $178.00  
  Purchase #4 $141.56   11.857%   $158.3448   $158.34   $158.35   $158.30  
  Purchase #5 $50.99   7.222%   $54.6725   $54.67   $54.65   $54.70  
  Purchase #6 $124.30   3.436%   $128.5709   $128.57   $128.55   $128.60  
  Purchase #7 $104.48   13.862%   $118.963   $118.96   $118.95   $119.00  
  7 purchase totals = $802.18       $869.9856   $869.98   $869.95   $869.90