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 $114.49   4.435%   $119.5676   $119.57   $119.55   $119.60  
  Purchase #2 $184.81   13.427%   $209.6244   $209.62   $209.60   $209.60  
  Purchase #3 $38.75   6.320%   $41.199   $41.20   $41.20   $41.20  
  Purchase #4 $23.96   6.574%   $25.5351   $25.54   $25.55   $25.50  
  Purchase #5 $96.79   5.298%   $101.9179   $101.92   $101.90   $101.90  
  Purchase #6 $88.80   6.494%   $94.5667   $94.57   $94.55   $94.60  
  Purchase #7 $178.70   8.800%   $194.4256   $194.43   $194.45   $194.40  
  7 purchase totals = $726.30       $786.8363   $786.85   $786.80   $786.80