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 $95.58   13.783%   $108.7538   $108.75   $108.75   $108.80  
  Purchase #2 $162.58   8.168%   $175.8595   $175.86   $175.85   $175.90  
  Purchase #3 $126.53   13.291%   $143.3471   $143.35   $143.35   $143.30  
  Purchase #4 $195.47   6.123%   $207.4386   $207.44   $207.45   $207.40  
  Purchase #5 $156.68   3.487%   $162.1434   $162.14   $162.15   $162.10  
  Purchase #6 $87.50   5.430%   $92.2513   $92.25   $92.25   $92.30  
  Purchase #7 $194.94   13.801%   $221.8437   $221.84   $221.85   $221.80  
  7 purchase totals = $1,019.28       $1,111.6374   $1,111.63   $1,111.65   $1,111.60