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 $58.52   9.252%   $63.9343   $63.93   $63.95   $63.90  
  Purchase #2 $236.72   11.626%   $264.2411   $264.24   $264.25   $264.20  
  Purchase #3 $139.67   13.349%   $158.3145   $158.31   $158.30   $158.30  
  Purchase #4 $68.54   9.243%   $74.8752   $74.88   $74.90   $74.90  
  Purchase #5 $161.29   9.298%   $176.2867   $176.29   $176.30   $176.30  
  Purchase #6 $26.55   13.649%   $30.1738   $30.17   $30.15   $30.20  
  Purchase #7 $124.99   4.205%   $130.2458   $130.25   $130.25   $130.20  
  7 purchase totals = $816.28       $898.0714   $898.07   $898.10   $898.00