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	$34.30	6.776%	$36.6242	$36.62	$36.60	$36.60
Purchase #2	$124.59	11.666%	$139.1247	$139.12	$139.10	$139.10
Purchase #3	$244.88	3.102%	$252.4762	$252.48	$252.50	$252.50
Purchase #4	$96.71	7.862%	$104.3133	$104.31	$104.30	$104.30
Purchase #5	$53.55	11.195%	$59.5449	$59.54	$59.55	$59.50
Purchase #6	$234.69	4.265%	$244.6995	$244.70	$244.70	$244.70
Purchase #7	$215.25	7.467%	$231.3227	$231.32	$231.30	$231.30
7 purchase totals =	$1,003.97		$1,068.1055	$1,068.09	$1,068.05	$1,068.00