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 $94.27   7.176%   $101.0348   $101.03   $101.05   $101.00  
  Purchase #2 $62.37   4.298%   $65.0507   $65.05   $65.05   $65.10  
  Purchase #3 $145.51   13.213%   $164.7362   $164.74   $164.75   $164.70  
  Purchase #4 $118.54   9.443%   $129.7337   $129.73   $129.75   $129.70  
  Purchase #5 $55.79   3.282%   $57.621   $57.62   $57.60   $57.60  
  Purchase #6 $196.45   6.353%   $208.9305   $208.93   $208.95   $208.90  
  Purchase #7 $148.93   12.863%   $168.0869   $168.09   $168.10   $168.10  
  7 purchase totals = $821.86       $895.1938   $895.19   $895.25   $895.10