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	$204.71	7.366%	$219.7889	$219.79	$219.80	$219.80
Purchase #2	$58.64	6.355%	$62.3666	$62.37	$62.35	$62.40
Purchase #3	$143.25	10.827%	$158.7597	$158.76	$158.75	$158.80
Purchase #4	$40.91	5.849%	$43.3028	$43.30	$43.30	$43.30
Purchase #5	$138.85	4.732%	$145.4204	$145.42	$145.40	$145.40
Purchase #6	$88.71	4.162%	$92.4021	$92.40	$92.40	$92.40
Purchase #7	$160.58	7.402%	$172.4661	$172.47	$172.45	$172.50
7 purchase totals =	$835.65		$894.5066	$894.51	$894.45	$894.60