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 $202.95   3.811%   $210.6844   $210.68   $210.70   $210.70  
  Purchase #2 $19.78   12.374%   $22.2276   $22.23   $22.25   $22.20  
  Purchase #3 $207.38   12.838%   $234.0034   $234.00   $234.00   $234.00  
  Purchase #4 $216.40   4.539%   $226.2224   $226.22   $226.20   $226.20  
  Purchase #5 $107.77   4.560%   $112.6843   $112.68   $112.70   $112.70  
  Purchase #6 $249.78   6.144%   $265.1265   $265.13   $265.15   $265.10  
  Purchase #7 $180.85   8.193%   $195.667   $195.67   $195.65   $195.70  
  7 purchase totals = $1,184.91       $1,266.6156   $1,266.61   $1,266.65   $1,266.60