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 $205.25   10.591%   $226.988   $226.99   $227.00   $227.00  
  Purchase #2 $92.26   12.674%   $103.953   $103.95   $103.95   $104.00  
  Purchase #3 $109.35   7.759%   $117.8345   $117.83   $117.85   $117.80  
  Purchase #4 $170.70   11.512%   $190.351   $190.35   $190.35   $190.40  
  Purchase #5 $80.95   3.708%   $83.9516   $83.95   $83.95   $84.00  
  Purchase #6 $8.27   9.611%   $9.0648   $9.06   $9.05   $9.10  
  Purchase #7 $209.89   5.327%   $221.0708   $221.07   $221.05   $221.10  
  7 purchase totals = $876.67       $953.2137   $953.20   $953.20   $953.40