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	$189.33	7.470%	$203.473	$203.47	$203.45	$203.50
Purchase #2	$167.45	3.248%	$172.8888	$172.89	$172.90	$172.90
Purchase #3	$209.56	10.162%	$230.8555	$230.86	$230.85	$230.90
Purchase #4	$194.69	5.462%	$205.324	$205.32	$205.30	$205.30
Purchase #5	$143.58	10.688%	$158.9258	$158.93	$158.95	$158.90
Purchase #6	$124.75	3.653%	$129.3071	$129.31	$129.30	$129.30
Purchase #7	$104.42	7.168%	$111.9048	$111.90	$111.90	$111.90
7 purchase totals =	$1,133.78		$1,212.6790	$1,212.68	$1,212.65	$1,212.70