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 $213.66   10.254%   $235.5687   $235.57   $235.55   $235.60  
  Purchase #2 $234.66   13.688%   $266.7803   $266.78   $266.80   $266.80  
  Purchase #3 $41.81   5.671%   $44.181   $44.18   $44.20   $44.20  
  Purchase #4 $195.73   6.863%   $209.1629   $209.16   $209.15   $209.20  
  Purchase #5 $197.64   8.378%   $214.1983   $214.20   $214.20   $214.20  
  Purchase #6 $239.68   11.839%   $268.0557   $268.06   $268.05   $268.10  
  Purchase #7 $27.84   6.541%   $29.661   $29.66   $29.65   $29.70  
  7 purchase totals = $1,151.02       $1,267.6079   $1,267.61   $1,267.60   $1,267.80