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	$193.41	13.399%	$219.325	$219.33	$219.35	$219.30
Purchase #2	$247.77	11.870%	$277.1803	$277.18	$277.20	$277.20
Purchase #3	$128.38	12.574%	$144.5225	$144.52	$144.50	$144.50
Purchase #4	$51.47	6.454%	$54.7919	$54.79	$54.80	$54.80
Purchase #5	$129.38	10.723%	$143.2534	$143.25	$143.25	$143.30
Purchase #6	$82.91	11.335%	$92.3078	$92.31	$92.30	$92.30
Purchase #7	$106.50	10.434%	$117.6122	$117.61	$117.60	$117.60
7 purchase totals =	$939.82		$1,048.9931	$1,048.99	$1,049.00	$1,049.00