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 $101.68   6.195%   $107.9791   $107.98   $108.00   $108.00  
  Purchase #2 $117.38   8.151%   $126.9476   $126.95   $126.95   $126.90  
  Purchase #3 $21.61   6.467%   $23.0075   $23.01   $23.00   $23.00  
  Purchase #4 $173.86   11.199%   $193.3306   $193.33   $193.35   $193.30  
  Purchase #5 $212.95   11.213%   $236.8281   $236.83   $236.85   $236.80  
  Purchase #6 $209.57   7.823%   $225.9647   $225.96   $225.95   $226.00  
  Purchase #7 $49.72   7.825%   $53.6106   $53.61   $53.60   $53.60  
  7 purchase totals = $886.77       $967.6682   $967.67   $967.70   $967.60