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 $192.62   10.403%   $212.6583   $212.66   $212.65   $212.70  
  Purchase #2 $195.47   5.601%   $206.4183   $206.42   $206.40   $206.40  
  Purchase #3 $130.71   6.194%   $138.8062   $138.81   $138.80   $138.80  
  Purchase #4 $209.54   13.718%   $238.2847   $238.28   $238.30   $238.30  
  Purchase #5 $233.97   9.273%   $255.666   $255.67   $255.65   $255.70  
  Purchase #6 $244.38   12.811%   $275.6875   $275.69   $275.70   $275.70  
  Purchase #7 $126.93   11.576%   $141.6234   $141.62   $141.60   $141.60  
  7 purchase totals = $1,333.62       $1,469.1444   $1,469.15   $1,469.10   $1,469.20