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 $62.85   10.540%   $69.4744   $69.47   $69.45   $69.50  
  Purchase #2 $14.38   9.754%   $15.7826   $15.78   $15.80   $15.80  
  Purchase #3 $174.44   12.169%   $195.6676   $195.67   $195.65   $195.70  
  Purchase #4 $218.82   12.281%   $245.6933   $245.69   $245.70   $245.70  
  Purchase #5 $131.63   5.755%   $139.2053   $139.21   $139.20   $139.20  
  Purchase #6 $70.78   8.261%   $76.6271   $76.63   $76.65   $76.60  
  Purchase #7 $191.47   6.110%   $203.1688   $203.17   $203.15   $203.20  
  7 purchase totals = $864.37       $945.6191   $945.62   $945.60   $945.70