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 $86.69   9.578%   $94.9932   $94.99   $95.00   $95.00  
  Purchase #2 $63.34   4.868%   $66.4234   $66.42   $66.40   $66.40  
  Purchase #3 $123.75   13.500%   $140.4563   $140.46   $140.45   $140.50  
  Purchase #4 $6.38   9.273%   $6.9716   $6.97   $6.95   $7.00  
  Purchase #5 $134.91   12.190%   $151.3555   $151.36   $151.35   $151.40  
  Purchase #6 $120.87   3.178%   $124.7112   $124.71   $124.70   $124.70  
  Purchase #7 $192.82   4.634%   $201.7553   $201.76   $201.75   $201.80  
  7 purchase totals = $728.76       $786.6665   $786.67   $786.60   $786.80