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	$98.85	5.501%	$104.2877	$104.29	$104.30	$104.30
Purchase #2	$248.64	9.134%	$271.3508	$271.35	$271.35	$271.40
Purchase #3	$235.34	13.247%	$266.5155	$266.52	$266.50	$266.50
Purchase #4	$231.64	6.778%	$247.3406	$247.34	$247.35	$247.30
Purchase #5	$37.38	13.848%	$42.5564	$42.56	$42.55	$42.60
Purchase #6	$75.72	3.742%	$78.5534	$78.55	$78.55	$78.60
Purchase #7	$48.55	11.495%	$54.1308	$54.13	$54.15	$54.10
7 purchase totals =	$976.12		$1,064.7352	$1,064.74	$1,064.75	$1,064.80