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	$242.98	6.195%	$258.0326	$258.03	$258.05	$258.00
Purchase #2	$11.75	5.575%	$12.4051	$12.41	$12.40	$12.40
Purchase #3	$202.92	10.541%	$224.3098	$224.31	$224.30	$224.30
Purchase #4	$148.71	11.248%	$165.4369	$165.44	$165.45	$165.40
Purchase #5	$48.75	11.520%	$54.366	$54.37	$54.35	$54.40
Purchase #6	$246.42	4.500%	$257.5089	$257.51	$257.50	$257.50
Purchase #7	$120.69	8.832%	$131.3493	$131.35	$131.35	$131.30
7 purchase totals =	$1,022.22		$1,103.4086	$1,103.42	$1,103.40	$1,103.30