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 $53.95   11.353%   $60.0749   $60.07   $60.05   $60.10  
  Purchase #2 $232.36   7.821%   $250.5329   $250.53   $250.55   $250.50  
  Purchase #3 $84.97   10.812%   $94.157   $94.16   $94.15   $94.20  
  Purchase #4 $82.68   12.158%   $92.7322   $92.73   $92.75   $92.70  
  Purchase #5 $206.75   3.787%   $214.5796   $214.58   $214.60   $214.60  
  Purchase #6 $167.61   13.424%   $190.11   $190.11   $190.10   $190.10  
  Purchase #7 $169.55   6.228%   $180.1096   $180.11   $180.10   $180.10  
  7 purchase totals = $997.87       $1,082.2962   $1,082.29   $1,082.30   $1,082.30