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	$139.74	8.591%	$151.7451	$151.75	$151.75	$151.70
Purchase #2	$19.84	5.127%	$20.8572	$20.86	$20.85	$20.90
Purchase #3	$150.32	13.869%	$171.1679	$171.17	$171.15	$171.20
Purchase #4	$39.60	13.536%	$44.9603	$44.96	$44.95	$45.00
Purchase #5	$153.35	12.624%	$172.7089	$172.71	$172.70	$172.70
Purchase #6	$49.69	11.702%	$55.5047	$55.50	$55.50	$55.50
Purchase #7	$185.83	12.394%	$208.8618	$208.86	$208.85	$208.90
7 purchase totals =	$738.37		$825.8059	$825.81	$825.75	$825.90