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 $65.57   4.646%   $68.6164   $68.62   $68.60   $68.60  
  Purchase #2 $167.54   10.228%   $184.676   $184.68   $184.70   $184.70  
  Purchase #3 $23.59   11.516%   $26.3066   $26.31   $26.30   $26.30  
  Purchase #4 $176.73   3.669%   $183.2142   $183.21   $183.20   $183.20  
  Purchase #5 $147.53   9.338%   $161.3064   $161.31   $161.30   $161.30  
  Purchase #6 $198.79   4.507%   $207.7495   $207.75   $207.75   $207.70  
  Purchase #7 $102.48   10.756%   $113.5027   $113.50   $113.50   $113.50  
  7 purchase totals = $882.23       $945.3718   $945.38   $945.35   $945.30