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 $89.50   6.260%   $95.1027   $95.10   $95.10   $95.10  
  Purchase #2 $62.61   7.532%   $67.3258   $67.33   $67.35   $67.30  
  Purchase #3 $216.60   12.663%   $244.0281   $244.03   $244.05   $244.00  
  Purchase #4 $51.28   12.523%   $57.7018   $57.70   $57.70   $57.70  
  Purchase #5 $50.83   9.161%   $55.4865   $55.49   $55.50   $55.50  
  Purchase #6 $167.67   4.560%   $175.3158   $175.32   $175.30   $175.30  
  Purchase #7 $13.76   10.322%   $15.1803   $15.18   $15.20   $15.20  
  7 purchase totals = $652.25       $710.1410   $710.15   $710.20   $710.10