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	$200.69	4.354%	$209.428	$209.43	$209.45	$209.40
Purchase #2	$90.35	11.635%	$100.8622	$100.86	$100.85	$100.90
Purchase #3	$177.39	4.394%	$185.1845	$185.18	$185.20	$185.20
Purchase #4	$225.80	9.482%	$247.2104	$247.21	$247.20	$247.20
Purchase #5	$211.86	9.399%	$231.7727	$231.77	$231.75	$231.80
Purchase #6	$37.77	13.837%	$42.9962	$43.00	$43.00	$43.00
Purchase #7	$38.57	3.438%	$39.896	$39.90	$39.90	$39.90
7 purchase totals =	$982.43		$1,057.3500	$1,057.35	$1,057.35	$1,057.40