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 $54.38   11.671%   $60.7267   $60.73   $60.75   $60.70  
  Purchase #2 $192.71   3.351%   $199.1677   $199.17   $199.15   $199.20  
  Purchase #3 $75.70   7.621%   $81.4691   $81.47   $81.45   $81.50  
  Purchase #4 $140.35   9.188%   $153.2454   $153.25   $153.25   $153.20  
  Purchase #5 $107.73   9.240%   $117.6843   $117.68   $117.70   $117.70  
  Purchase #6 $221.29   9.157%   $241.5535   $241.55   $241.55   $241.60  
  Purchase #7 $228.49   9.335%   $249.8195   $249.82   $249.80   $249.80  
  7 purchase totals = $1,020.65       $1,103.6662   $1,103.67   $1,103.65   $1,103.70