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	$244.87	3.443%	$253.3009	$253.30	$253.30	$253.30
Purchase #2	$10.82	10.328%	$11.9375	$11.94	$11.95	$11.90
Purchase #3	$16.84	4.458%	$17.5907	$17.59	$17.60	$17.60
Purchase #4	$54.71	9.405%	$59.8555	$59.86	$59.85	$59.90
Purchase #5	$220.88	13.275%	$250.2018	$250.20	$250.20	$250.20
Purchase #6	$162.84	6.388%	$173.2422	$173.24	$173.25	$173.20
Purchase #7	$104.72	11.428%	$116.6874	$116.69	$116.70	$116.70
7 purchase totals =	$815.68		$882.8160	$882.82	$882.85	$882.80