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 $182.70   6.753%   $195.0377   $195.04   $195.05   $195.00  
  Purchase #2 $47.26   11.784%   $52.8291   $52.83   $52.85   $52.80  
  Purchase #3 $19.86   13.854%   $22.6114   $22.61   $22.60   $22.60  
  Purchase #4 $16.68   13.498%   $18.9315   $18.93   $18.95   $18.90  
  Purchase #5 $84.27   10.766%   $93.3425   $93.34   $93.35   $93.30  
  Purchase #6 $33.44   13.708%   $38.024   $38.02   $38.00   $38.00  
  Purchase #7 $184.30   13.214%   $208.6534   $208.65   $208.65   $208.70  
  7 purchase totals = $568.51       $629.4296   $629.42   $629.45   $629.30