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	$214.49	3.760%	$222.5548	$222.55	$222.55	$222.60
Purchase #2	$211.31	9.105%	$230.5498	$230.55	$230.55	$230.50
Purchase #3	$95.48	3.865%	$99.1703	$99.17	$99.15	$99.20
Purchase #4	$176.31	11.493%	$196.5733	$196.57	$196.55	$196.60
Purchase #5	$210.77	11.550%	$235.1139	$235.11	$235.10	$235.10
Purchase #6	$96.89	8.321%	$104.9522	$104.95	$104.95	$105.00
Purchase #7	$221.72	8.280%	$240.0784	$240.08	$240.10	$240.10
7 purchase totals =	$1,226.97		$1,328.9927	$1,328.98	$1,328.95	$1,329.10