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 $163.82   7.715%   $176.4587   $176.46   $176.45   $176.50  
  Purchase #2 $227.76   7.483%   $244.8033   $244.80   $244.80   $244.80  
  Purchase #3 $59.52   13.677%   $67.6606   $67.66   $67.65   $67.70  
  Purchase #4 $105.67   5.644%   $111.634   $111.63   $111.65   $111.60  
  Purchase #5 $65.52   12.263%   $73.5547   $73.55   $73.55   $73.60  
  Purchase #6 $210.89   13.468%   $239.2927   $239.29   $239.30   $239.30  
  Purchase #7 $45.34   8.848%   $49.3517   $49.35   $49.35   $49.40  
  7 purchase totals = $878.52       $962.7557   $962.74   $962.75   $962.90