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 $33.95   3.173%   $35.0272   $35.03   $35.05   $35.00  
  Purchase #2 $59.76   12.641%   $67.3143   $67.31   $67.30   $67.30  
  Purchase #3 $109.32   13.411%   $123.9809   $123.98   $124.00   $124.00  
  Purchase #4 $92.35   6.104%   $97.987   $97.99   $98.00   $98.00  
  Purchase #5 $5.27   10.367%   $5.8163   $5.82   $5.80   $5.80  
  Purchase #6 $63.35   5.138%   $66.6049   $66.60   $66.60   $66.60  
  Purchase #7 $80.91   7.191%   $86.7282   $86.73   $86.75   $86.70  
  7 purchase totals = $444.91       $483.4588   $483.46   $483.50   $483.40