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 $119.72   4.802%   $125.469   $125.47   $125.45   $125.50  
  Purchase #2 $163.82   7.355%   $175.869   $175.87   $175.85   $175.90  
  Purchase #3 $127.57   7.374%   $136.977   $136.98   $137.00   $137.00  
  Purchase #4 $205.88   4.475%   $215.0931   $215.09   $215.10   $215.10  
  Purchase #5 $34.29   6.147%   $36.3978   $36.40   $36.40   $36.40  
  Purchase #6 $245.43   12.163%   $275.2817   $275.28   $275.30   $275.30  
  Purchase #7 $225.50   10.302%   $248.731   $248.73   $248.75   $248.70  
  7 purchase totals = $1,122.21       $1,213.8186   $1,213.82   $1,213.85   $1,213.90