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	$62.94	13.859%	$71.6629	$71.66	$71.65	$71.70
Purchase #2	$95.54	6.142%	$101.4081	$101.41	$101.40	$101.40
Purchase #3	$134.51	7.361%	$144.4113	$144.41	$144.40	$144.40
Purchase #4	$86.49	4.463%	$90.35	$90.35	$90.35	$90.40
Purchase #5	$114.33	10.772%	$126.6456	$126.65	$126.65	$126.60
Purchase #6	$80.63	11.784%	$90.1314	$90.13	$90.15	$90.10
Purchase #7	$143.69	5.388%	$151.432	$151.43	$151.45	$151.40
7 purchase totals =	$718.13		$776.0413	$776.04	$776.05	$776.00