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	$87.60	4.783%	$91.7899	$91.79	$91.80	$91.80
Purchase #2	$118.85	7.561%	$127.8362	$127.84	$127.85	$127.80
Purchase #3	$93.43	6.160%	$99.1853	$99.19	$99.20	$99.20
Purchase #4	$226.46	3.136%	$233.5618	$233.56	$233.55	$233.60
Purchase #5	$69.92	12.116%	$78.3915	$78.39	$78.40	$78.40
Purchase #6	$15.27	7.184%	$16.367	$16.37	$16.35	$16.40
Purchase #7	$101.61	9.713%	$111.4794	$111.48	$111.50	$111.50
7 purchase totals =	$713.14		$758.6111	$758.62	$758.65	$758.70