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	$127.75	10.859%	$141.6224	$141.62	$141.60	$141.60
Purchase #2	$108.51	7.740%	$116.9087	$116.91	$116.90	$116.90
Purchase #3	$176.93	9.244%	$193.2854	$193.29	$193.30	$193.30
Purchase #4	$144.54	12.325%	$162.3546	$162.35	$162.35	$162.40
Purchase #5	$152.43	8.597%	$165.5344	$165.53	$165.55	$165.50
Purchase #6	$90.45	11.278%	$100.651	$100.65	$100.65	$100.70
Purchase #7	$208.49	5.165%	$219.2585	$219.26	$219.25	$219.30
7 purchase totals =	$1,009.10		$1,099.6150	$1,099.61	$1,099.60	$1,099.70