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 $244.36   9.264%   $266.9975   $267.00   $267.00   $267.00  
  Purchase #2 $36.77   6.689%   $39.2295   $39.23   $39.25   $39.20  
  Purchase #3 $6.28   5.280%   $6.6116   $6.61   $6.60   $6.60  
  Purchase #4 $11.34   6.757%   $12.1062   $12.11   $12.10   $12.10  
  Purchase #5 $31.64   11.355%   $35.2327   $35.23   $35.25   $35.20  
  Purchase #6 $146.29   7.610%   $157.4227   $157.42   $157.40   $157.40  
  Purchase #7 $233.92   4.662%   $244.8254   $244.83   $244.85   $244.80  
  7 purchase totals = $710.60       $762.4256   $762.43   $762.45   $762.30