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	$195.84	10.224%	$215.8627	$215.86	$215.85	$215.90
Purchase #2	$178.37	11.722%	$199.2785	$199.28	$199.30	$199.30
Purchase #3	$153.84	5.419%	$162.1766	$162.18	$162.20	$162.20
Purchase #4	$225.94	13.208%	$255.7822	$255.78	$255.80	$255.80
Purchase #5	$126.49	8.499%	$137.2404	$137.24	$137.25	$137.20
Purchase #6	$173.35	4.636%	$181.3865	$181.39	$181.40	$181.40
Purchase #7	$100.34	9.219%	$109.5903	$109.59	$109.60	$109.60
7 purchase totals =	$1,154.17		$1,261.3172	$1,261.32	$1,261.40	$1,261.40