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	$123.52	3.417%	$127.7407	$127.74	$127.75	$127.70
Purchase #2	$9.84	13.599%	$11.1781	$11.18	$11.20	$11.20
Purchase #3	$229.60	10.693%	$254.1511	$254.15	$254.15	$254.20
Purchase #4	$97.51	4.595%	$101.9906	$101.99	$102.00	$102.00
Purchase #5	$88.43	13.380%	$100.2619	$100.26	$100.25	$100.30
Purchase #6	$193.77	7.471%	$208.2466	$208.25	$208.25	$208.20
Purchase #7	$130.78	6.192%	$138.8779	$138.88	$138.90	$138.90
7 purchase totals =	$873.45		$942.4469	$942.45	$942.50	$942.50