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	$125.89	4.715%	$131.8257	$131.83	$131.85	$131.80
Purchase #2	$217.42	5.682%	$229.7738	$229.77	$229.75	$229.80
Purchase #3	$14.78	3.771%	$15.3374	$15.34	$15.35	$15.30
Purchase #4	$246.51	10.577%	$272.5834	$272.58	$272.60	$272.60
Purchase #5	$87.84	3.309%	$90.7466	$90.75	$90.75	$90.70
Purchase #6	$95.29	5.454%	$100.4871	$100.49	$100.50	$100.50
Purchase #7	$50.69	5.581%	$53.519	$53.52	$53.50	$53.50
7 purchase totals =	$838.42		$894.2730	$894.28	$894.30	$894.20