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	$44.29	3.191%	$45.7033	$45.70	$45.70	$45.70
Purchase #2	$173.95	10.371%	$191.9904	$191.99	$192.00	$192.00
Purchase #3	$158.34	10.269%	$174.5999	$174.60	$174.60	$174.60
Purchase #4	$102.68	8.461%	$111.3678	$111.37	$111.35	$111.40
Purchase #5	$80.81	13.569%	$91.7751	$91.78	$91.80	$91.80
Purchase #6	$224.53	13.758%	$255.4208	$255.42	$255.40	$255.40
Purchase #7	$28.58	13.402%	$32.4103	$32.41	$32.40	$32.40
7 purchase totals =	$813.18		$903.2676	$903.27	$903.25	$903.30