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	$64.41	12.844%	$72.6828	$72.68	$72.70	$72.70
Purchase #2	$38.79	4.853%	$40.6725	$40.67	$40.65	$40.70
Purchase #3	$92.45	13.727%	$105.1406	$105.14	$105.15	$105.10
Purchase #4	$89.28	12.771%	$100.6819	$100.68	$100.70	$100.70
Purchase #5	$235.61	3.320%	$243.4323	$243.43	$243.45	$243.40
Purchase #6	$47.71	10.707%	$52.8183	$52.82	$52.80	$52.80
Purchase #7	$106.84	12.552%	$120.2506	$120.25	$120.25	$120.30
7 purchase totals =	$675.09		$735.6790	$735.67	$735.70	$735.70