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	$153.27	3.276%	$158.2911	$158.29	$158.30	$158.30
Purchase #2	$43.54	4.871%	$45.6608	$45.66	$45.65	$45.70
Purchase #3	$204.46	6.336%	$217.4146	$217.41	$217.40	$217.40
Purchase #4	$122.27	4.449%	$127.7098	$127.71	$127.70	$127.70
Purchase #5	$242.66	5.417%	$255.8049	$255.80	$255.80	$255.80
Purchase #6	$115.58	8.778%	$125.7256	$125.73	$125.75	$125.70
Purchase #7	$91.26	10.255%	$100.6187	$100.62	$100.60	$100.60
7 purchase totals =	$973.04		$1,031.2255	$1,031.22	$1,031.20	$1,031.20