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	$133.39	10.422%	$147.2919	$147.29	$147.30	$147.30
Purchase #2	$122.34	7.718%	$131.7822	$131.78	$131.80	$131.80
Purchase #3	$219.71	10.489%	$242.7554	$242.76	$242.75	$242.80
Purchase #4	$238.84	3.858%	$248.0544	$248.05	$248.05	$248.10
Purchase #5	$32.96	5.863%	$34.8924	$34.89	$34.90	$34.90
Purchase #6	$211.91	8.150%	$229.1807	$229.18	$229.20	$229.20
Purchase #7	$59.25	8.747%	$64.4326	$64.43	$64.45	$64.40
7 purchase totals =	$1,018.40		$1,098.3896	$1,098.38	$1,098.45	$1,098.50