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 $69.45   9.522%   $76.063   $76.06   $76.05   $76.10  
  Purchase #2 $15.64   5.566%   $16.5105   $16.51   $16.50   $16.50  
  Purchase #3 $195.89   6.696%   $209.0068   $209.01   $209.00   $209.00  
  Purchase #4 $5.35   10.113%   $5.891   $5.89   $5.90   $5.90  
  Purchase #5 $233.53   3.612%   $241.9651   $241.97   $241.95   $242.00  
  Purchase #6 $11.67   8.688%   $12.6839   $12.68   $12.70   $12.70  
  Purchase #7 $172.97   12.367%   $194.3612   $194.36   $194.35   $194.40  
  7 purchase totals = $704.50       $756.4815   $756.48   $756.45   $756.60