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 $171.44   13.304%   $194.2484   $194.25   $194.25   $194.20  
  Purchase #2 $249.30   13.781%   $283.656   $283.66   $283.65   $283.70  
  Purchase #3 $87.81   5.800%   $92.903   $92.90   $92.90   $92.90  
  Purchase #4 $32.54   7.601%   $35.0134   $35.01   $35.00   $35.00  
  Purchase #5 $218.34   12.426%   $245.4709   $245.47   $245.45   $245.50  
  Purchase #6 $226.82   4.379%   $236.7524   $236.75   $236.75   $236.80  
  Purchase #7 $165.59   8.868%   $180.2745   $180.27   $180.25   $180.30  
  7 purchase totals = $1,151.84       $1,268.3186   $1,268.31   $1,268.25   $1,268.40