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 $39.85   10.679%   $44.1056   $44.11   $44.10   $44.10  
  Purchase #2 $115.73   9.135%   $126.3019   $126.30   $126.30   $126.30  
  Purchase #3 $151.68   10.789%   $168.0448   $168.04   $168.05   $168.00  
  Purchase #4 $57.64   4.614%   $60.2995   $60.30   $60.30   $60.30  
  Purchase #5 $54.69   12.323%   $61.4294   $61.43   $61.45   $61.40  
  Purchase #6 $54.56   3.463%   $56.4494   $56.45   $56.45   $56.40  
  Purchase #7 $199.93   8.504%   $216.932   $216.93   $216.95   $216.90  
  7 purchase totals = $674.08       $733.5626   $733.56   $733.60   $733.40