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	$144.33	9.149%	$157.5348	$157.53	$157.55	$157.50
Purchase #2	$223.47	4.539%	$233.6133	$233.61	$233.60	$233.60
Purchase #3	$216.60	11.323%	$241.1256	$241.13	$241.15	$241.10
Purchase #4	$72.38	11.103%	$80.4164	$80.42	$80.40	$80.40
Purchase #5	$127.38	13.379%	$144.4222	$144.42	$144.40	$144.40
Purchase #6	$67.84	11.295%	$75.5025	$75.50	$75.50	$75.50
Purchase #7	$96.86	9.856%	$106.4065	$106.41	$106.40	$106.40
7 purchase totals =	$948.86		$1,039.0213	$1,039.02	$1,039.00	$1,038.90