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	$146.29	8.526%	$158.7627	$158.76	$158.75	$158.80
Purchase #2	$99.89	3.654%	$103.54	$103.54	$103.55	$103.50
Purchase #3	$246.40	13.438%	$279.5112	$279.51	$279.50	$279.50
Purchase #4	$240.28	9.130%	$262.2176	$262.22	$262.20	$262.20
Purchase #5	$114.64	4.656%	$119.9776	$119.98	$120.00	$120.00
Purchase #6	$114.26	3.713%	$118.5025	$118.50	$118.50	$118.50
Purchase #7	$234.32	13.151%	$265.1354	$265.14	$265.15	$265.10
7 purchase totals =	$1,196.08		$1,307.6470	$1,307.65	$1,307.65	$1,307.60