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	$213.46	4.388%	$222.8266	$222.83	$222.85	$222.80
Purchase #2	$227.38	7.597%	$244.6541	$244.65	$244.65	$244.70
Purchase #3	$158.87	8.346%	$172.1293	$172.13	$172.15	$172.10
Purchase #4	$129.88	13.719%	$147.6982	$147.70	$147.70	$147.70
Purchase #5	$241.72	8.822%	$263.0445	$263.04	$263.05	$263.00
Purchase #6	$99.71	13.241%	$112.9126	$112.91	$112.90	$112.90
Purchase #7	$43.40	11.337%	$48.3203	$48.32	$48.30	$48.30
7 purchase totals =	$1,114.42		$1,211.5856	$1,211.58	$1,211.60	$1,211.50