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	$143.39	5.726%	$151.6005	$151.60	$151.60	$151.60
Purchase #2	$77.66	4.126%	$80.8643	$80.86	$80.85	$80.90
Purchase #3	$40.96	10.813%	$45.389	$45.39	$45.40	$45.40
Purchase #4	$141.81	5.137%	$149.0948	$149.09	$149.10	$149.10
Purchase #5	$23.68	6.651%	$25.255	$25.26	$25.25	$25.30
Purchase #6	$235.92	3.715%	$244.6844	$244.68	$244.70	$244.70
Purchase #7	$104.96	6.218%	$111.4864	$111.49	$111.50	$111.50
7 purchase totals =	$768.38		$808.3744	$808.37	$808.40	$808.50