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 $247.46   5.263%   $260.4838   $260.48   $260.50   $260.50  
  Purchase #2 $198.61   5.487%   $209.5077   $209.51   $209.50   $209.50  
  Purchase #3 $9.25   10.771%   $10.2463   $10.25   $10.25   $10.20  
  Purchase #4 $186.82   4.719%   $195.636   $195.64   $195.65   $195.60  
  Purchase #5 $148.73   5.711%   $157.224   $157.22   $157.20   $157.20  
  Purchase #6 $154.47   5.208%   $162.5148   $162.51   $162.50   $162.50  
  Purchase #7 $139.50   13.364%   $158.1428   $158.14   $158.15   $158.10  
  7 purchase totals = $1,084.84       $1,153.7554   $1,153.75   $1,153.75   $1,153.60