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	$143.45	9.332%	$156.8368	$156.84	$156.85	$156.80
Purchase #2	$79.59	13.528%	$90.3569	$90.36	$90.35	$90.40
Purchase #3	$163.27	10.390%	$180.2338	$180.23	$180.25	$180.20
Purchase #4	$9.33	12.716%	$10.5164	$10.52	$10.50	$10.50
Purchase #5	$107.45	9.862%	$118.0467	$118.05	$118.05	$118.00
Purchase #6	$98.76	4.590%	$103.2931	$103.29	$103.30	$103.30
Purchase #7	$123.74	3.638%	$128.2417	$128.24	$128.25	$128.20
7 purchase totals =	$725.59		$787.5254	$787.53	$787.55	$787.40