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	$188.76	6.261%	$200.5783	$200.58	$200.60	$200.60
Purchase #2	$63.39	11.735%	$70.8288	$70.83	$70.85	$70.80
Purchase #3	$185.37	3.866%	$192.5364	$192.54	$192.55	$192.50
Purchase #4	$16.86	5.418%	$17.7735	$17.77	$17.75	$17.80
Purchase #5	$94.77	4.693%	$99.2176	$99.22	$99.20	$99.20
Purchase #6	$217.38	3.719%	$225.4644	$225.46	$225.45	$225.50
Purchase #7	$243.59	11.661%	$271.995	$272.00	$272.00	$272.00
7 purchase totals =	$1,010.12		$1,078.3940	$1,078.40	$1,078.40	$1,078.40