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 $86.96   9.305%   $95.0516   $95.05   $95.05   $95.10  
  Purchase #2 $20.49   13.668%   $23.2906   $23.29   $23.30   $23.30  
  Purchase #3 $85.28   13.173%   $96.5139   $96.51   $96.50   $96.50  
  Purchase #4 $110.33   12.305%   $123.9061   $123.91   $123.90   $123.90  
  Purchase #5 $206.90   3.505%   $214.1518   $214.15   $214.15   $214.20  
  Purchase #6 $101.64   8.607%   $110.3882   $110.39   $110.40   $110.40  
  Purchase #7 $153.62   5.813%   $162.5499   $162.55   $162.55   $162.50  
  7 purchase totals = $765.22       $825.8521   $825.85   $825.85   $825.90