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	$165.85	12.643%	$186.8184	$186.82	$186.80	$186.80
Purchase #2	$235.42	4.317%	$245.5831	$245.58	$245.60	$245.60
Purchase #3	$91.91	8.207%	$99.4531	$99.45	$99.45	$99.50
Purchase #4	$101.53	12.407%	$114.1268	$114.13	$114.15	$114.10
Purchase #5	$177.28	5.855%	$187.6597	$187.66	$187.65	$187.70
Purchase #6	$240.97	6.147%	$255.7824	$255.78	$255.80	$255.80
Purchase #7	$17.37	12.395%	$19.523	$19.52	$19.50	$19.50
7 purchase totals =	$1,030.33		$1,108.9465	$1,108.94	$1,108.95	$1,109.00