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	$128.45	10.363%	$141.7613	$141.76	$141.75	$141.80
Purchase #2	$212.89	8.185%	$230.315	$230.32	$230.30	$230.30
Purchase #3	$9.96	5.450%	$10.5028	$10.50	$10.50	$10.50
Purchase #4	$86.58	6.448%	$92.1627	$92.16	$92.15	$92.20
Purchase #5	$74.61	11.432%	$83.1394	$83.14	$83.15	$83.10
Purchase #6	$72.87	6.673%	$77.7326	$77.73	$77.75	$77.70
Purchase #7	$99.51	12.405%	$111.8542	$111.85	$111.85	$111.90
7 purchase totals =	$684.87		$747.4680	$747.46	$747.45	$747.50