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	$126.27	3.411%	$130.5771	$130.58	$130.60	$130.60
Purchase #2	$42.95	11.767%	$48.0039	$48.00	$48.00	$48.00
Purchase #3	$62.32	8.322%	$67.5063	$67.51	$67.50	$67.50
Purchase #4	$56.71	10.687%	$62.7706	$62.77	$62.75	$62.80
Purchase #5	$42.28	7.827%	$45.5893	$45.59	$45.60	$45.60
Purchase #6	$46.29	8.348%	$50.1543	$50.15	$50.15	$50.20
Purchase #7	$211.35	3.774%	$219.3263	$219.33	$219.35	$219.30
7 purchase totals =	$588.17		$623.9278	$623.93	$623.95	$624.00