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	$148.88	6.534%	$158.6078	$158.61	$158.60	$158.60
Purchase #2	$140.51	13.255%	$159.1346	$159.13	$159.15	$159.10
Purchase #3	$88.59	12.319%	$99.5034	$99.50	$99.50	$99.50
Purchase #4	$121.49	13.522%	$137.9179	$137.92	$137.90	$137.90
Purchase #5	$130.29	8.237%	$141.022	$141.02	$141.00	$141.00
Purchase #6	$93.90	9.794%	$103.0966	$103.10	$103.10	$103.10
Purchase #7	$138.47	6.129%	$146.9568	$146.96	$146.95	$147.00
7 purchase totals =	$862.13		$946.2391	$946.24	$946.20	$946.20