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	$115.94	9.795%	$127.2963	$127.30	$127.30	$127.30
Purchase #2	$19.61	13.761%	$22.3085	$22.31	$22.30	$22.30
Purchase #3	$199.41	13.408%	$226.1469	$226.15	$226.15	$226.10
Purchase #4	$224.50	3.613%	$232.6112	$232.61	$232.60	$232.60
Purchase #5	$140.96	3.846%	$146.3813	$146.38	$146.40	$146.40
Purchase #6	$241.56	12.439%	$271.6076	$271.61	$271.60	$271.60
Purchase #7	$64.51	12.416%	$72.5196	$72.52	$72.50	$72.50
7 purchase totals =	$1,006.49		$1,098.8714	$1,098.88	$1,098.85	$1,098.80