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	$53.47	6.478%	$56.9338	$56.93	$56.95	$56.90
Purchase #2	$220.77	4.291%	$230.2432	$230.24	$230.25	$230.20
Purchase #3	$122.25	13.363%	$138.5863	$138.59	$138.60	$138.60
Purchase #4	$91.98	9.322%	$100.5544	$100.55	$100.55	$100.60
Purchase #5	$52.74	12.603%	$59.3868	$59.39	$59.40	$59.40
Purchase #6	$144.83	6.740%	$154.5915	$154.59	$154.60	$154.60
Purchase #7	$131.45	7.505%	$141.3153	$141.32	$141.30	$141.30
7 purchase totals =	$817.49		$881.6113	$881.61	$881.65	$881.60