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 $69.48   9.538%   $76.107   $76.11   $76.10   $76.10  
  Purchase #2 $87.47   6.486%   $93.1433   $93.14   $93.15   $93.10  
  Purchase #3 $146.94   7.810%   $158.416   $158.42   $158.40   $158.40  
  Purchase #4 $216.83   8.363%   $234.9635   $234.96   $234.95   $235.00  
  Purchase #5 $35.47   4.546%   $37.0825   $37.08   $37.10   $37.10  
  Purchase #6 $187.27   4.599%   $195.8825   $195.88   $195.90   $195.90  
  Purchase #7 $198.93   11.282%   $221.3733   $221.37   $221.35   $221.40  
  7 purchase totals = $942.39       $1,016.9681   $1,016.96   $1,016.95   $1,017.00