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 $177.88   4.726%   $186.2866   $186.29   $186.30   $186.30  
  Purchase #2 $154.93   9.432%   $169.543   $169.54   $169.55   $169.50  
  Purchase #3 $175.97   13.605%   $199.9107   $199.91   $199.90   $199.90  
  Purchase #4 $60.28   5.396%   $63.5327   $63.53   $63.55   $63.50  
  Purchase #5 $36.47   6.528%   $38.8508   $38.85   $38.85   $38.90  
  Purchase #6 $95.31   9.618%   $104.4769   $104.48   $104.50   $104.50  
  Purchase #7 $125.27   6.404%   $133.2923   $133.29   $133.30   $133.30  
  7 purchase totals = $826.11       $895.8930   $895.89   $895.95   $895.90