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	$225.55	4.436%	$235.5554	$235.56	$235.55	$235.60
Purchase #2	$221.57	7.231%	$237.5917	$237.59	$237.60	$237.60
Purchase #3	$100.62	10.760%	$111.4467	$111.45	$111.45	$111.40
Purchase #4	$169.67	5.198%	$178.4894	$178.49	$178.50	$178.50
Purchase #5	$47.85	5.461%	$50.4631	$50.46	$50.45	$50.50
Purchase #6	$245.78	10.742%	$272.1817	$272.18	$272.20	$272.20
Purchase #7	$169.72	6.319%	$180.4446	$180.44	$180.45	$180.40
7 purchase totals =	$1,180.76		$1,266.1726	$1,266.17	$1,266.20	$1,266.20