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 $205.45   10.366%   $226.7469   $226.75   $226.75   $226.70  
  Purchase #2 $232.95   9.726%   $255.6067   $255.61   $255.60   $255.60  
  Purchase #3 $239.51   6.342%   $254.6997   $254.70   $254.70   $254.70  
  Purchase #4 $109.99   7.745%   $118.5087   $118.51   $118.50   $118.50  
  Purchase #5 $32.89   11.660%   $36.725   $36.73   $36.75   $36.70  
  Purchase #6 $146.47   3.736%   $151.9421   $151.94   $151.95   $151.90  
  Purchase #7 $94.33   12.375%   $106.0033   $106.00   $106.00   $106.00  
  7 purchase totals = $1,061.59       $1,150.2324   $1,150.24   $1,150.25   $1,150.10