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	$143.56	6.792%	$153.3106	$153.31	$153.30	$153.30
Purchase #2	$146.65	10.549%	$162.1201	$162.12	$162.10	$162.10
Purchase #3	$89.77	3.483%	$92.8967	$92.90	$92.90	$92.90
Purchase #4	$238.36	11.544%	$265.8763	$265.88	$265.90	$265.90
Purchase #5	$226.42	10.174%	$249.456	$249.46	$249.45	$249.50
Purchase #6	$12.61	10.390%	$13.9202	$13.92	$13.90	$13.90
Purchase #7	$13.72	6.412%	$14.5997	$14.60	$14.60	$14.60
7 purchase totals =	$871.09		$952.1796	$952.19	$952.15	$952.20