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 $107.95   7.872%   $116.4478   $116.45   $116.45   $116.40  
  Purchase #2 $101.91   7.234%   $109.2822   $109.28   $109.30   $109.30  
  Purchase #3 $34.70   5.653%   $36.6616   $36.66   $36.65   $36.70  
  Purchase #4 $236.44   7.256%   $253.5961   $253.60   $253.60   $253.60  
  Purchase #5 $43.53   12.736%   $49.074   $49.07   $49.05   $49.10  
  Purchase #6 $50.60   10.672%   $56   $56.00   $56.00   $56.00  
  Purchase #7 $75.91   13.292%   $86   $86.00   $86.00   $86.00  
  7 purchase totals = $651.04       $707.0617   $707.06   $707.05   $707.10