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	$226.43	12.429%	$254.573	$254.57	$254.55	$254.60
Purchase #2	$37.40	12.607%	$42.115	$42.12	$42.10	$42.10
Purchase #3	$247.52	3.122%	$255.2476	$255.25	$255.25	$255.20
Purchase #4	$239.30	3.624%	$247.9722	$247.97	$247.95	$248.00
Purchase #5	$225.31	4.255%	$234.8969	$234.90	$234.90	$234.90
Purchase #6	$221.77	5.321%	$233.5704	$233.57	$233.55	$233.60
Purchase #7	$118.31	7.447%	$127.1205	$127.12	$127.10	$127.10
7 purchase totals =	$1,316.04		$1,395.4956	$1,395.50	$1,395.40	$1,395.50