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	$44.41	3.437%	$45.9364	$45.94	$45.95	$45.90
Purchase #2	$155.45	11.853%	$173.8755	$173.88	$173.90	$173.90
Purchase #3	$10.47	6.565%	$11.1574	$11.16	$11.15	$11.20
Purchase #4	$92.51	10.208%	$101.9534	$101.95	$101.95	$102.00
Purchase #5	$76.28	7.725%	$82.1726	$82.17	$82.15	$82.20
Purchase #6	$124.32	4.471%	$129.8783	$129.88	$129.90	$129.90
Purchase #7	$154.73	9.380%	$169.2437	$169.24	$169.25	$169.20
7 purchase totals =	$658.17		$714.2173	$714.22	$714.25	$714.30