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	$197.40	4.307%	$205.902	$205.90	$205.90	$205.90
Purchase #2	$204.83	11.519%	$228.4244	$228.42	$228.40	$228.40
Purchase #3	$127.84	7.644%	$137.6121	$137.61	$137.60	$137.60
Purchase #4	$105.28	6.243%	$111.8526	$111.85	$111.85	$111.90
Purchase #5	$240.31	13.355%	$272.4034	$272.40	$272.40	$272.40
Purchase #6	$15.42	13.473%	$17.4975	$17.50	$17.50	$17.50
Purchase #7	$83.72	8.248%	$90.6252	$90.63	$90.65	$90.60
7 purchase totals =	$974.80		$1,064.3172	$1,064.31	$1,064.30	$1,064.30