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 $119.62   5.827%   $126.5903   $126.59   $126.60   $126.60  
  Purchase #2 $105.73   11.190%   $117.5612   $117.56   $117.55   $117.60  
  Purchase #3 $59.51   5.470%   $62.7652   $62.77   $62.75   $62.80  
  Purchase #4 $164.44   5.778%   $173.9413   $173.94   $173.95   $173.90  
  Purchase #5 $172.36   13.344%   $195.3597   $195.36   $195.35   $195.40  
  Purchase #6 $167.69   13.823%   $190.8698   $190.87   $190.85   $190.90  
  Purchase #7 $63.44   10.642%   $70.1913   $70.19   $70.20   $70.20  
  7 purchase totals = $852.79       $937.2788   $937.28   $937.25   $937.40