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	$143.35	5.487%	$151.2156	$151.22	$151.20	$151.20
Purchase #2	$224.51	6.271%	$238.589	$238.59	$238.60	$238.60
Purchase #3	$216.37	12.245%	$242.8645	$242.86	$242.85	$242.90
Purchase #4	$18.92	6.415%	$20.1337	$20.13	$20.15	$20.10
Purchase #5	$201.28	6.746%	$214.8583	$214.86	$214.85	$214.90
Purchase #6	$42.49	5.447%	$44.8044	$44.80	$44.80	$44.80
Purchase #7	$138.83	11.693%	$155.0634	$155.06	$155.05	$155.10
7 purchase totals =	$985.75		$1,067.5289	$1,067.52	$1,067.50	$1,067.60