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	$212.90	7.593%	$229.0655	$229.07	$229.05	$229.10
Purchase #2	$43.45	3.753%	$45.0807	$45.08	$45.10	$45.10
Purchase #3	$111.41	3.619%	$115.4419	$115.44	$115.45	$115.40
Purchase #4	$18.37	7.196%	$19.6919	$19.69	$19.70	$19.70
Purchase #5	$143.25	6.856%	$153.0712	$153.07	$153.05	$153.10
Purchase #6	$223.77	13.691%	$254.4064	$254.41	$254.40	$254.40
Purchase #7	$100.49	10.632%	$111.1741	$111.17	$111.15	$111.20
7 purchase totals =	$853.64		$927.9317	$927.93	$927.90	$928.00