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 $85.33   8.823%   $92.8587   $92.86   $92.85   $92.90  
  Purchase #2 $69.97   4.828%   $73.3482   $73.35   $73.35   $73.30  
  Purchase #3 $127.73   4.293%   $133.2134   $133.21   $133.20   $133.20  
  Purchase #4 $163.88   5.574%   $173.0147   $173.01   $173.00   $173.00  
  Purchase #5 $157.91   6.128%   $167.5867   $167.59   $167.60   $167.60  
  Purchase #6 $114.96   3.155%   $118.587   $118.59   $118.60   $118.60  
  Purchase #7 $184.83   3.492%   $191.2843   $191.28   $191.30   $191.30  
  7 purchase totals = $904.61       $949.8930   $949.89   $949.90   $949.90