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	$127.42	12.593%	$143.466	$143.47	$143.45	$143.50
Purchase #2	$241.34	13.672%	$274.336	$274.34	$274.35	$274.30
Purchase #3	$79.51	5.218%	$83.6588	$83.66	$83.65	$83.70
Purchase #4	$186.43	6.365%	$198.2963	$198.30	$198.30	$198.30
Purchase #5	$165.51	3.463%	$171.2416	$171.24	$171.25	$171.20
Purchase #6	$87.92	10.155%	$96.8483	$96.85	$96.85	$96.80
Purchase #7	$91.69	13.470%	$104.0406	$104.04	$104.05	$104.00
7 purchase totals =	$979.82		$1,071.8876	$1,071.90	$1,071.90	$1,071.80