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	$144.86	9.250%	$158.2596	$158.26	$158.25	$158.30
Purchase #2	$12.28	6.592%	$13.0895	$13.09	$13.10	$13.10
Purchase #3	$127.42	3.523%	$131.909	$131.91	$131.90	$131.90
Purchase #4	$173.41	6.205%	$184.1701	$184.17	$184.15	$184.20
Purchase #5	$129.43	11.679%	$144.5461	$144.55	$144.55	$144.50
Purchase #6	$100.70	8.706%	$109.4669	$109.47	$109.45	$109.50
Purchase #7	$130.68	9.150%	$142.6372	$142.64	$142.65	$142.60
7 purchase totals =	$818.78		$884.0784	$884.09	$884.05	$884.10