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 $153.95   9.522%   $168.6091   $168.61   $168.60   $168.60  
  Purchase #2 $182.25   4.419%   $190.3036   $190.30   $190.30   $190.30  
  Purchase #3 $21.31   11.711%   $23.8056   $23.81   $23.80   $23.80  
  Purchase #4 $97.58   10.159%   $107.4932   $107.49   $107.50   $107.50  
  Purchase #5 $34.93   12.222%   $39.1991   $39.20   $39.20   $39.20  
  Purchase #6 $27.83   7.653%   $29.9598   $29.96   $29.95   $30.00  
  Purchase #7 $51.87   5.333%   $54.6362   $54.64   $54.65   $54.60  
  7 purchase totals = $569.72       $614.0066   $614.01   $614.00   $614.00