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 $201.26   3.450%   $208.2035   $208.20   $208.20   $208.20  
  Purchase #2 $87.47   8.794%   $95.1621   $95.16   $95.15   $95.20  
  Purchase #3 $56.57   7.658%   $60.9021   $60.90   $60.90   $60.90  
  Purchase #4 $49.56   3.339%   $51.2148   $51.21   $51.20   $51.20  
  Purchase #5 $94.78   4.168%   $98.7304   $98.73   $98.75   $98.70  
  Purchase #6 $66.28   13.374%   $75.1443   $75.14   $75.15   $75.10  
  Purchase #7 $80.68   7.748%   $86.9311   $86.93   $86.95   $86.90  
  7 purchase totals = $636.60       $676.2883   $676.27   $676.30   $676.20