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 $95.95   10.158%   $105.6966   $105.70   $105.70   $105.70  
  Purchase #2 $6.54   5.514%   $6.9006   $6.90   $6.90   $6.90  
  Purchase #3 $34.78   12.739%   $39.2106   $39.21   $39.20   $39.20  
  Purchase #4 $57.60   6.692%   $61.4546   $61.45   $61.45   $61.50  
  Purchase #5 $140.54   12.314%   $157.8461   $157.85   $157.85   $157.80  
  Purchase #6 $15.30   10.601%   $16.922   $16.92   $16.90   $16.90  
  Purchase #7 $24.42   3.362%   $25.241   $25.24   $25.25   $25.20  
  7 purchase totals = $375.13       $413.2715   $413.27   $413.25   $413.20