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	$43.60	3.861%	$45.2834	$45.28	$45.30	$45.30
Purchase #2	$198.85	11.867%	$222.4475	$222.45	$222.45	$222.40
Purchase #3	$165.71	4.205%	$172.6781	$172.68	$172.70	$172.70
Purchase #4	$138.74	3.123%	$143.0729	$143.07	$143.05	$143.10
Purchase #5	$119.90	5.369%	$126.3374	$126.34	$126.35	$126.30
Purchase #6	$106.97	12.160%	$119.9776	$119.98	$120.00	$120.00
Purchase #7	$87.69	12.198%	$98.3864	$98.39	$98.40	$98.40
7 purchase totals =	$861.46		$928.1833	$928.19	$928.25	$928.20