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 $215.34   9.857%   $236.5661   $236.57   $236.55   $236.60  
  Purchase #2 $54.53   8.835%   $59.3477   $59.35   $59.35   $59.30  
  Purchase #3 $5.45   9.517%   $5.9687   $5.97   $5.95   $6.00  
  Purchase #4 $147.48   6.357%   $156.8553   $156.86   $156.85   $156.90  
  Purchase #5 $99.73   5.866%   $105.5802   $105.58   $105.60   $105.60  
  Purchase #6 $166.93   5.382%   $175.9142   $175.91   $175.90   $175.90  
  Purchase #7 $15.68   9.283%   $17.1356   $17.14   $17.15   $17.10  
  7 purchase totals = $705.14       $757.3678   $757.38   $757.35   $757.40