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	$37.41	7.613%	$40.258	$40.26	$40.25	$40.30
Purchase #2	$235.94	7.778%	$254.2914	$254.29	$254.30	$254.30
Purchase #3	$149.35	12.436%	$167.9232	$167.92	$167.90	$167.90
Purchase #4	$139.63	10.694%	$154.562	$154.56	$154.55	$154.60
Purchase #5	$108.36	7.552%	$116.5433	$116.54	$116.55	$116.50
Purchase #6	$225.41	11.669%	$251.7131	$251.71	$251.70	$251.70
Purchase #7	$56.43	5.431%	$59.4947	$59.49	$59.50	$59.50
7 purchase totals =	$952.53		$1,044.7857	$1,044.77	$1,044.75	$1,044.80