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 $69.26   9.355%   $75.7393   $75.74   $75.75   $75.70  
  Purchase #2 $151.83   11.239%   $168.8942   $168.89   $168.90   $168.90  
  Purchase #3 $34.79   6.624%   $37.0945   $37.09   $37.10   $37.10  
  Purchase #4 $27.72   10.687%   $30.6824   $30.68   $30.70   $30.70  
  Purchase #5 $28.97   12.191%   $32.5017   $32.50   $32.50   $32.50  
  Purchase #6 $57.63   12.656%   $64.9237   $64.92   $64.90   $64.90  
  Purchase #7 $53.91   5.594%   $56.9257   $56.93   $56.95   $56.90  
  7 purchase totals = $424.11       $466.7615   $466.75   $466.80   $466.70