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	$155.58	13.239%	$176.1772	$176.18	$176.20	$176.20
Purchase #2	$97.61	8.560%	$105.9654	$105.97	$105.95	$106.00
Purchase #3	$31.72	3.817%	$32.9308	$32.93	$32.95	$32.90
Purchase #4	$115.73	9.787%	$127.0565	$127.06	$127.05	$127.10
Purchase #5	$92.85	8.574%	$100.811	$100.81	$100.80	$100.80
Purchase #6	$39.81	6.598%	$42.4367	$42.44	$42.45	$42.40
Purchase #7	$26.87	6.208%	$28.5381	$28.54	$28.55	$28.50
7 purchase totals =	$560.17		$613.9157	$613.93	$613.95	$613.90