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	$18.37	3.182%	$18.9545	$18.95	$18.95	$19.00
Purchase #2	$172.44	3.471%	$178.4254	$178.43	$178.45	$178.40
Purchase #3	$244.39	13.804%	$278.1256	$278.13	$278.15	$278.10
Purchase #4	$72.51	8.699%	$78.8176	$78.82	$78.80	$78.80
Purchase #5	$174.52	7.292%	$187.246	$187.25	$187.25	$187.20
Purchase #6	$232.35	3.861%	$241.321	$241.32	$241.30	$241.30
Purchase #7	$66.73	13.766%	$75.9161	$75.92	$75.90	$75.90
7 purchase totals =	$981.31		$1,058.8062	$1,058.82	$1,058.80	$1,058.70