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	$209.67	6.429%	$223.1497	$223.15	$223.15	$223.10
Purchase #2	$92.31	8.832%	$100.4628	$100.46	$100.45	$100.50
Purchase #3	$34.92	11.418%	$38.9072	$38.91	$38.90	$38.90
Purchase #4	$89.87	3.425%	$92.948	$92.95	$92.95	$92.90
Purchase #5	$195.91	5.593%	$206.8672	$206.87	$206.85	$206.90
Purchase #6	$172.97	8.518%	$187.7036	$187.70	$187.70	$187.70
Purchase #7	$112.60	13.347%	$127.6287	$127.63	$127.65	$127.60
7 purchase totals =	$908.25		$977.6672	$977.67	$977.65	$977.60