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	$227.67	11.350%	$253.5105	$253.51	$253.50	$253.50
Purchase #2	$173.75	9.721%	$190.6402	$190.64	$190.65	$190.60
Purchase #3	$210.50	10.464%	$232.5267	$232.53	$232.55	$232.50
Purchase #4	$40.96	3.810%	$42.5206	$42.52	$42.50	$42.50
Purchase #5	$116.35	6.823%	$124.2886	$124.29	$124.30	$124.30
Purchase #6	$97.99	13.814%	$111.5263	$111.53	$111.55	$111.50
Purchase #7	$114.93	10.717%	$127.247	$127.25	$127.25	$127.20
7 purchase totals =	$982.15		$1,082.2599	$1,082.27	$1,082.30	$1,082.10