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	$202.91	10.683%	$224.5869	$224.59	$224.60	$224.60
Purchase #2	$100.70	8.513%	$109.2726	$109.27	$109.25	$109.30
Purchase #3	$104.86	6.350%	$111.5186	$111.52	$111.50	$111.50
Purchase #4	$232.65	3.452%	$240.6811	$240.68	$240.70	$240.70
Purchase #5	$208.83	11.447%	$232.7348	$232.73	$232.75	$232.70
Purchase #6	$225.71	4.394%	$235.6277	$235.63	$235.65	$235.60
Purchase #7	$152.32	5.151%	$160.166	$160.17	$160.15	$160.20
7 purchase totals =	$1,227.98		$1,314.5877	$1,314.59	$1,314.60	$1,314.60