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	$66.56	12.114%	$74.6231	$74.62	$74.60	$74.60
Purchase #2	$161.54	9.325%	$176.6036	$176.60	$176.60	$176.60
Purchase #3	$132.89	13.573%	$150.9272	$150.93	$150.95	$150.90
Purchase #4	$226.69	3.505%	$234.6355	$234.64	$234.65	$234.60
Purchase #5	$103.41	13.613%	$117.4872	$117.49	$117.50	$117.50
Purchase #6	$211.98	4.424%	$221.358	$221.36	$221.35	$221.40
Purchase #7	$39.62	9.671%	$43.4517	$43.45	$43.45	$43.50
7 purchase totals =	$942.69		$1,019.0863	$1,019.09	$1,019.10	$1,019.10