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	$179.83	5.236%	$189.2459	$189.25	$189.25	$189.20
Purchase #2	$137.30	12.654%	$154.6739	$154.67	$154.65	$154.70
Purchase #3	$34.47	9.292%	$37.673	$37.67	$37.65	$37.70
Purchase #4	$100.59	10.114%	$110.7637	$110.76	$110.75	$110.80
Purchase #5	$146.90	13.571%	$166.8358	$166.84	$166.85	$166.80
Purchase #6	$163.63	5.152%	$172.0602	$172.06	$172.05	$172.10
Purchase #7	$157.32	4.390%	$164.2263	$164.23	$164.25	$164.20
7 purchase totals =	$920.04		$995.4788	$995.48	$995.45	$995.50