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	$238.63	12.273%	$267.9171	$267.92	$267.90	$267.90
Purchase #2	$39.68	6.824%	$42.3878	$42.39	$42.40	$42.40
Purchase #3	$240.35	10.395%	$265.3344	$265.33	$265.35	$265.30
Purchase #4	$141.92	8.627%	$154.1634	$154.16	$154.15	$154.20
Purchase #5	$32.49	4.788%	$34.0456	$34.05	$34.05	$34.00
Purchase #6	$138.39	13.841%	$157.5446	$157.54	$157.55	$157.50
Purchase #7	$123.25	3.627%	$127.7203	$127.72	$127.70	$127.70
7 purchase totals =	$954.71		$1,049.1132	$1,049.11	$1,049.10	$1,049.00