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	$238.88	6.764%	$255.0378	$255.04	$255.05	$255.00
Purchase #2	$67.78	4.113%	$70.5678	$70.57	$70.55	$70.60
Purchase #3	$195.68	9.815%	$214.886	$214.89	$214.90	$214.90
Purchase #4	$223.80	11.317%	$249.1274	$249.13	$249.15	$249.10
Purchase #5	$12.83	12.310%	$14.4094	$14.41	$14.40	$14.40
Purchase #6	$222.50	5.268%	$234.2213	$234.22	$234.20	$234.20
Purchase #7	$127.32	5.358%	$134.1418	$134.14	$134.15	$134.10
7 purchase totals =	$1,088.79		$1,172.3915	$1,172.40	$1,172.40	$1,172.30