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	$196.31	10.541%	$217.003	$217.00	$217.00	$217.00
Purchase #2	$79.60	3.633%	$82.4919	$82.49	$82.50	$82.50
Purchase #3	$98.68	13.318%	$111.8222	$111.82	$111.80	$111.80
Purchase #4	$210.37	9.253%	$229.8355	$229.84	$229.85	$229.80
Purchase #5	$148.57	3.217%	$153.3495	$153.35	$153.35	$153.30
Purchase #6	$244.42	11.535%	$272.6138	$272.61	$272.60	$272.60
Purchase #7	$107.67	13.539%	$122.2474	$122.25	$122.25	$122.20
7 purchase totals =	$1,085.62		$1,189.3633	$1,189.36	$1,189.35	$1,189.20