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	$57.72	3.286%	$59.6167	$59.62	$59.60	$59.60
Purchase #2	$10.57	5.686%	$11.171	$11.17	$11.15	$11.20
Purchase #3	$110.55	3.480%	$114.3971	$114.40	$114.40	$114.40
Purchase #4	$160.56	11.325%	$178.7434	$178.74	$178.75	$178.70
Purchase #5	$228.45	11.242%	$254.1323	$254.13	$254.15	$254.10
Purchase #6	$242.41	3.657%	$251.2749	$251.27	$251.25	$251.30
Purchase #7	$84.94	6.427%	$90.3991	$90.40	$90.40	$90.40
7 purchase totals =	$895.20		$959.7345	$959.73	$959.70	$959.70