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	$167.80	3.130%	$173.0521	$173.05	$173.05	$173.10
Purchase #2	$158.57	5.141%	$166.7221	$166.72	$166.70	$166.70
Purchase #3	$249.30	7.699%	$268.4936	$268.49	$268.50	$268.50
Purchase #4	$110.56	10.456%	$122.1202	$122.12	$122.10	$122.10
Purchase #5	$133.40	7.620%	$143.5651	$143.57	$143.55	$143.60
Purchase #6	$98.57	13.476%	$111.8533	$111.85	$111.85	$111.90
Purchase #7	$233.62	3.435%	$241.6448	$241.64	$241.65	$241.60
7 purchase totals =	$1,151.82		$1,227.4512	$1,227.44	$1,227.40	$1,227.50