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	$23.40	9.630%	$25.6534	$25.65	$25.65	$25.70
Purchase #2	$163.88	10.357%	$180.8531	$180.85	$180.85	$180.90
Purchase #3	$103.51	7.479%	$111.2515	$111.25	$111.25	$111.30
Purchase #4	$17.28	12.388%	$19.4206	$19.42	$19.40	$19.40
Purchase #5	$22.92	7.243%	$24.5801	$24.58	$24.60	$24.60
Purchase #6	$100.94	6.842%	$107.8463	$107.85	$107.85	$107.80
Purchase #7	$183.41	7.151%	$196.5256	$196.53	$196.55	$196.50
7 purchase totals =	$615.34		$666.1306	$666.13	$666.15	$666.20