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	$226.44	6.491%	$241.1382	$241.14	$241.15	$241.10
Purchase #2	$226.86	13.655%	$257.8377	$257.84	$257.85	$257.80
Purchase #3	$241.60	3.562%	$250.2058	$250.21	$250.20	$250.20
Purchase #4	$74.66	10.382%	$82.4112	$82.41	$82.40	$82.40
Purchase #5	$82.25	12.767%	$92.7509	$92.75	$92.75	$92.80
Purchase #6	$99.42	13.123%	$112.4669	$112.47	$112.45	$112.50
Purchase #7	$131.76	10.391%	$145.4512	$145.45	$145.45	$145.50
7 purchase totals =	$1,082.99		$1,182.2619	$1,182.27	$1,182.25	$1,182.30