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	$199.77	6.339%	$212.4334	$212.43	$212.45	$212.40
Purchase #2	$101.31	8.131%	$109.5475	$109.55	$109.55	$109.50
Purchase #3	$145.52	12.808%	$164.1582	$164.16	$164.15	$164.20
Purchase #4	$141.85	11.658%	$158.3869	$158.39	$158.40	$158.40
Purchase #5	$55.29	11.423%	$61.6058	$61.61	$61.60	$61.60
Purchase #6	$241.46	4.364%	$251.9973	$252.00	$252.00	$252.00
Purchase #7	$10.84	13.717%	$12.3269	$12.33	$12.35	$12.30
7 purchase totals =	$896.04		$970.4560	$970.47	$970.50	$970.40