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 $183.36   6.457%   $195.1996   $195.20   $195.20   $195.20  
  Purchase #2 $215.30   3.315%   $222.4372   $222.44   $222.45   $222.40  
  Purchase #3 $103.78   7.128%   $111.1774   $111.18   $111.20   $111.20  
  Purchase #4 $231.90   8.203%   $250.9228   $250.92   $250.90   $250.90  
  Purchase #5 $189.84   12.684%   $213.9193   $213.92   $213.90   $213.90  
  Purchase #6 $242.39   10.253%   $267.2422   $267.24   $267.25   $267.20  
  Purchase #7 $92.87   11.405%   $103.4618   $103.46   $103.45   $103.50  
  7 purchase totals = $1,259.44       $1,364.3603   $1,364.36   $1,364.35   $1,364.30