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	$155.42	5.271%	$163.6122	$163.61	$163.60	$163.60
Purchase #2	$19.66	3.107%	$20.2708	$20.27	$20.25	$20.30
Purchase #3	$41.31	10.616%	$45.6955	$45.70	$45.70	$45.70
Purchase #4	$11.49	4.570%	$12.0151	$12.02	$12.00	$12.00
Purchase #5	$236.29	7.688%	$254.456	$254.46	$254.45	$254.50
Purchase #6	$87.37	3.607%	$90.5214	$90.52	$90.50	$90.50
Purchase #7	$54.67	8.251%	$59.1808	$59.18	$59.20	$59.20
7 purchase totals =	$606.21		$645.7518	$645.76	$645.70	$645.80