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	$216.81	5.810%	$229.4067	$229.41	$229.40	$229.40
Purchase #2	$173.47	10.653%	$191.9498	$191.95	$191.95	$191.90
Purchase #3	$242.48	3.672%	$251.3839	$251.38	$251.40	$251.40
Purchase #4	$64.96	8.244%	$70.3153	$70.32	$70.30	$70.30
Purchase #5	$42.30	7.860%	$45.6248	$45.62	$45.60	$45.60
Purchase #6	$79.33	12.401%	$89.1677	$89.17	$89.15	$89.20
Purchase #7	$64.94	9.105%	$70.8528	$70.85	$70.85	$70.90
7 purchase totals =	$884.29		$948.7010	$948.70	$948.65	$948.70