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	$157.60	13.316%	$178.586	$178.59	$178.60	$178.60
Purchase #2	$15.83	11.362%	$17.6286	$17.63	$17.65	$17.60
Purchase #3	$40.41	6.812%	$43.1627	$43.16	$43.15	$43.20
Purchase #4	$59.34	5.768%	$62.7627	$62.76	$62.75	$62.80
Purchase #5	$153.82	5.496%	$162.2739	$162.27	$162.25	$162.30
Purchase #6	$79.63	5.294%	$83.8456	$83.85	$83.85	$83.80
Purchase #7	$247.44	7.174%	$265.1913	$265.19	$265.20	$265.20
7 purchase totals =	$754.07		$813.4508	$813.45	$813.45	$813.50