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 $43.82   4.567%   $45.8213   $45.82   $45.80   $45.80  
  Purchase #2 $114.69   11.368%   $127.728   $127.73   $127.75   $127.70  
  Purchase #3 $137.89   11.672%   $153.9845   $153.98   $154.00   $154.00  
  Purchase #4 $178.58   7.798%   $192.5057   $192.51   $192.50   $192.50  
  Purchase #5 $10.37   6.418%   $11.0355   $11.04   $11.05   $11.00  
  Purchase #6 $21.94   7.520%   $23.5899   $23.59   $23.60   $23.60  
  Purchase #7 $193.75   4.394%   $202.2634   $202.26   $202.25   $202.30  
  7 purchase totals = $701.04       $756.9283   $756.93   $756.95   $756.90