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	$138.92	9.841%	$152.5911	$152.59	$152.60	$152.60
Purchase #2	$208.48	3.319%	$215.3995	$215.40	$215.40	$215.40
Purchase #3	$66.96	6.615%	$71.3894	$71.39	$71.40	$71.40
Purchase #4	$19.42	12.425%	$21.8329	$21.83	$21.85	$21.80
Purchase #5	$241.76	11.852%	$270.4134	$270.41	$270.40	$270.40
Purchase #6	$155.93	4.230%	$162.5258	$162.53	$162.55	$162.50
Purchase #7	$109.68	12.102%	$122.9535	$122.95	$122.95	$123.00
7 purchase totals =	$941.15		$1,017.1056	$1,017.10	$1,017.15	$1,017.10