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	$21.69	3.522%	$22.4539	$22.45	$22.45	$22.50
Purchase #2	$89.51	11.223%	$99.5557	$99.56	$99.55	$99.60
Purchase #3	$127.93	5.363%	$134.7909	$134.79	$134.80	$134.80
Purchase #4	$19.67	9.377%	$21.5145	$21.51	$21.50	$21.50
Purchase #5	$230.86	4.399%	$241.0155	$241.02	$241.00	$241.00
Purchase #6	$121.55	4.142%	$126.5846	$126.58	$126.60	$126.60
Purchase #7	$134.58	10.154%	$148.2453	$148.25	$148.25	$148.20
7 purchase totals =	$745.79		$794.1604	$794.16	$794.15	$794.20