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	$196.84	9.112%	$214.7761	$214.78	$214.80	$214.80
Purchase #2	$245.56	13.766%	$279.3638	$279.36	$279.35	$279.40
Purchase #3	$179.53	6.481%	$191.1653	$191.17	$191.15	$191.20
Purchase #4	$138.82	3.376%	$143.5066	$143.51	$143.50	$143.50
Purchase #5	$97.72	12.274%	$109.7142	$109.71	$109.70	$109.70
Purchase #6	$233.50	3.733%	$242.2166	$242.22	$242.20	$242.20
Purchase #7	$121.58	8.487%	$131.8985	$131.90	$131.90	$131.90
7 purchase totals =	$1,213.55		$1,312.6411	$1,312.65	$1,312.60	$1,312.70