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	$227.76	6.359%	$242.2433	$242.24	$242.25	$242.20
Purchase #2	$96.81	3.487%	$100.1858	$100.19	$100.20	$100.20
Purchase #3	$242.58	5.806%	$256.6642	$256.66	$256.65	$256.70
Purchase #4	$159.47	8.430%	$172.9133	$172.91	$172.90	$172.90
Purchase #5	$158.41	7.410%	$170.1482	$170.15	$170.15	$170.10
Purchase #6	$40.85	6.787%	$43.6225	$43.62	$43.60	$43.60
Purchase #7	$247.42	8.790%	$269.1682	$269.17	$269.15	$269.20
7 purchase totals =	$1,173.30		$1,254.9455	$1,254.94	$1,254.90	$1,254.90