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	$156.52	5.749%	$165.5183	$165.52	$165.50	$165.50
Purchase #2	$96.79	11.833%	$108.2432	$108.24	$108.25	$108.20
Purchase #3	$102.31	8.529%	$111.036	$111.04	$111.05	$111.00
Purchase #4	$227.42	12.453%	$255.7406	$255.74	$255.75	$255.70
Purchase #5	$137.54	11.686%	$153.6129	$153.61	$153.60	$153.60
Purchase #6	$149.86	3.258%	$154.7424	$154.74	$154.75	$154.70
Purchase #7	$159.36	8.176%	$172.3893	$172.39	$172.40	$172.40
7 purchase totals =	$1,029.80		$1,121.2827	$1,121.28	$1,121.30	$1,121.10