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	$59.55	6.466%	$63.4005	$63.40	$63.40	$63.40
Purchase #2	$96.57	7.430%	$103.7452	$103.75	$103.75	$103.70
Purchase #3	$17.87	7.481%	$19.2069	$19.21	$19.20	$19.20
Purchase #4	$79.99	13.240%	$90.5807	$90.58	$90.60	$90.60
Purchase #5	$74.73	5.557%	$78.8827	$78.88	$78.90	$78.90
Purchase #6	$41.92	8.350%	$45.4203	$45.42	$45.40	$45.40
Purchase #7	$142.82	11.528%	$159.2843	$159.28	$159.30	$159.30
7 purchase totals =	$513.45		$560.5206	$560.52	$560.55	$560.50