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 $175.59   10.260%   $193.6055   $193.61   $193.60   $193.60  
  Purchase #2 $178.91   8.548%   $194.2032   $194.20   $194.20   $194.20  
  Purchase #3 $15.98   13.824%   $18.1891   $18.19   $18.20   $18.20  
  Purchase #4 $241.36   12.545%   $271.6386   $271.64   $271.65   $271.60  
  Purchase #5 $53.25   11.393%   $59.3168   $59.32   $59.30   $59.30  
  Purchase #6 $62.74   7.170%   $67.2385   $67.24   $67.25   $67.20  
  Purchase #7 $58.71   7.295%   $62.9929   $62.99   $63.00   $63.00  
  7 purchase totals = $786.54       $867.1846   $867.19   $867.20   $867.10