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 $46.71   11.671%   $52.1615   $52.16   $52.15   $52.20  
  Purchase #2 $143.42   12.764%   $161.7261   $161.73   $161.75   $161.70  
  Purchase #3 $24.89   6.481%   $26.5031   $26.50   $26.50   $26.50  
  Purchase #4 $11.68   6.328%   $12.4191   $12.42   $12.40   $12.40  
  Purchase #5 $172.81   9.176%   $188.667   $188.67   $188.65   $188.70  
  Purchase #6 $228.86   6.277%   $243.2255   $243.23   $243.25   $243.20  
  Purchase #7 $73.96   3.183%   $76.3141   $76.31   $76.30   $76.30  
  7 purchase totals = $702.33       $761.0164   $761.02   $761.00   $761.00