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	$39.41	4.740%	$41.278	$41.28	$41.30	$41.30
Purchase #2	$70.68	6.771%	$75.4657	$75.47	$75.45	$75.50
Purchase #3	$141.27	12.418%	$158.8129	$158.81	$158.80	$158.80
Purchase #4	$125.88	5.516%	$132.8235	$132.82	$132.80	$132.80
Purchase #5	$122.81	3.532%	$127.1476	$127.15	$127.15	$127.10
Purchase #6	$29.88	10.712%	$33.0807	$33.08	$33.10	$33.10
Purchase #7	$76.35	8.224%	$82.629	$82.63	$82.65	$82.60
7 purchase totals =	$606.28		$651.2374	$651.24	$651.25	$651.20