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	$243.30	8.252%	$263.3771	$263.38	$263.40	$263.40
Purchase #2	$132.60	10.757%	$146.8638	$146.86	$146.85	$146.90
Purchase #3	$111.83	6.781%	$119.4132	$119.41	$119.40	$119.40
Purchase #4	$109.96	7.825%	$118.5644	$118.56	$118.55	$118.60
Purchase #5	$244.54	11.103%	$271.6913	$271.69	$271.70	$271.70
Purchase #6	$76.39	13.688%	$86.8463	$86.85	$86.85	$86.80
Purchase #7	$145.95	6.408%	$155.3025	$155.30	$155.30	$155.30
7 purchase totals =	$1,064.57		$1,162.0586	$1,162.05	$1,162.05	$1,162.10