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	$100.44	3.798%	$104.2547	$104.25	$104.25	$104.30
Purchase #2	$242.52	5.410%	$255.6403	$255.64	$255.65	$255.60
Purchase #3	$143.45	3.781%	$148.8738	$148.87	$148.85	$148.90
Purchase #4	$126.73	12.815%	$142.9704	$142.97	$142.95	$143.00
Purchase #5	$205.75	6.505%	$219.134	$219.13	$219.15	$219.10
Purchase #6	$98.34	8.382%	$106.5829	$106.58	$106.60	$106.60
Purchase #7	$155.75	11.489%	$173.6441	$173.64	$173.65	$173.60
7 purchase totals =	$1,072.98		$1,151.1002	$1,151.08	$1,151.10	$1,151.10