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 $195.76   6.623%   $208.7252   $208.73   $208.75   $208.70  
  Purchase #2 $31.95   13.104%   $36.1367   $36.14   $36.15   $36.10  
  Purchase #3 $175.38   7.226%   $188.053   $188.05   $188.05   $188.10  
  Purchase #4 $178.64   9.321%   $195.291   $195.29   $195.30   $195.30  
  Purchase #5 $178.61   13.848%   $203.3439   $203.34   $203.35   $203.30  
  Purchase #6 $23.29   12.343%   $26.1647   $26.16   $26.15   $26.20  
  Purchase #7 $192.99   5.848%   $204.2761   $204.28   $204.30   $204.30  
  7 purchase totals = $976.62       $1,061.9906   $1,061.99   $1,062.05   $1,062.00