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 $58.69   4.809%   $61.5124   $61.51   $61.50   $61.50  
  Purchase #2 $126.99   8.806%   $138.1727   $138.17   $138.15   $138.20  
  Purchase #3 $178.66   5.231%   $188.0057   $188.01   $188.00   $188.00  
  Purchase #4 $88.89   6.815%   $94.9479   $94.95   $94.95   $94.90  
  Purchase #5 $17.54   8.667%   $19.0602   $19.06   $19.05   $19.10  
  Purchase #6 $215.84   4.459%   $225.4643   $225.46   $225.45   $225.50  
  Purchase #7 $49.70   10.183%   $54.761   $54.76   $54.75   $54.80  
  7 purchase totals = $736.31       $781.9242   $781.92   $781.85   $782.00