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	$176.68	13.357%	$200.2791	$200.28	$200.30	$200.30
Purchase #2	$11.34	6.236%	$12.0472	$12.05	$12.05	$12.00
Purchase #3	$166.55	3.734%	$172.769	$172.77	$172.75	$172.80
Purchase #4	$43.82	13.797%	$49.8658	$49.87	$49.85	$49.90
Purchase #5	$240.61	13.366%	$272.7699	$272.77	$272.75	$272.80
Purchase #6	$133.93	13.491%	$151.9985	$152.00	$152.00	$152.00
Purchase #7	$120.73	5.372%	$127.2156	$127.22	$127.20	$127.20
7 purchase totals =	$893.66		$986.9451	$986.96	$986.90	$987.00