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 $112.29   11.851%   $125.5975   $125.60   $125.60   $125.60  
  Purchase #2 $20.69   5.872%   $21.9049   $21.90   $21.90   $21.90  
  Purchase #3 $169.42   11.166%   $188.3374   $188.34   $188.35   $188.30  
  Purchase #4 $32.58   13.388%   $36.9418   $36.94   $36.95   $36.90  
  Purchase #5 $205.97   10.190%   $226.9583   $226.96   $226.95   $227.00  
  Purchase #6 $109.60   13.539%   $124.4387   $124.44   $124.45   $124.40  
  Purchase #7 $134.65   13.188%   $152.4076   $152.41   $152.40   $152.40  
  7 purchase totals = $785.20       $876.5862   $876.59   $876.60   $876.50