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 $141.60   7.598%   $152.3588   $152.36   $152.35   $152.40  
  Purchase #2 $202.25   3.503%   $209.3348   $209.33   $209.35   $209.30  
  Purchase #3 $134.54   5.703%   $142.2128   $142.21   $142.20   $142.20  
  Purchase #4 $45.58   13.260%   $51.6239   $51.62   $51.60   $51.60  
  Purchase #5 $63.39   12.212%   $71.1312   $71.13   $71.15   $71.10  
  Purchase #6 $216.54   11.642%   $241.7496   $241.75   $241.75   $241.70  
  Purchase #7 $159.77   9.541%   $175.0137   $175.01   $175.00   $175.00  
  7 purchase totals = $963.67       $1,043.4248   $1,043.41   $1,043.40   $1,043.30