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 $92.63   4.425%   $96.7289   $96.73   $96.75   $96.70  
  Purchase #2 $24.41   9.588%   $26.7504   $26.75   $26.75   $26.80  
  Purchase #3 $101.58   11.524%   $113.2861   $113.29   $113.30   $113.30  
  Purchase #4 $33.49   3.242%   $34.5757   $34.58   $34.60   $34.60  
  Purchase #5 $231.79   10.439%   $255.9866   $255.99   $256.00   $256.00  
  Purchase #6 $90.28   10.698%   $99.9382   $99.94   $99.95   $99.90  
  Purchase #7 $93.80   11.609%   $104.6892   $104.69   $104.70   $104.70  
  7 purchase totals = $667.98       $731.9551   $731.97   $732.05   $732.00