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 $103.41   10.341%   $114.1036   $114.10   $114.10   $114.10  
  Purchase #2 $38.88   12.111%   $43.5888   $43.59   $43.60   $43.60  
  Purchase #3 $117.53   5.370%   $123.8414   $123.84   $123.85   $123.80  
  Purchase #4 $28.98   5.604%   $30.604   $30.60   $30.60   $30.60  
  Purchase #5 $191.46   7.811%   $206.4149   $206.41   $206.40   $206.40  
  Purchase #6 $149.93   5.148%   $157.6484   $157.65   $157.65   $157.60  
  Purchase #7 $233.93   10.638%   $258.8155   $258.82   $258.80   $258.80  
  7 purchase totals = $864.12       $935.0166   $935.01   $935.00   $934.90