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 $94.59   8.626%   $102.7493   $102.75   $102.75   $102.70  
  Purchase #2 $207.89   3.380%   $214.9167   $214.92   $214.90   $214.90  
  Purchase #3 $136.43   5.127%   $143.4248   $143.42   $143.40   $143.40  
  Purchase #4 $224.50   4.295%   $234.1423   $234.14   $234.15   $234.10  
  Purchase #5 $152.59   10.318%   $168.3342   $168.33   $168.35   $168.30  
  Purchase #6 $34.75   5.729%   $36.7408   $36.74   $36.75   $36.70  
  Purchase #7 $22.60   11.647%   $25.2322   $25.23   $25.25   $25.20  
  7 purchase totals = $873.35       $925.5403   $925.53   $925.55   $925.30