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	$99.87	13.810%	$113.662	$113.66	$113.65	$113.70
Purchase #2	$96.69	11.593%	$107.8993	$107.90	$107.90	$107.90
Purchase #3	$32.38	3.205%	$33.4178	$33.42	$33.40	$33.40
Purchase #4	$85.67	5.237%	$90.1565	$90.16	$90.15	$90.20
Purchase #5	$152.70	8.391%	$165.5131	$165.51	$165.50	$165.50
Purchase #6	$139.37	10.725%	$154.3174	$154.32	$154.30	$154.30
Purchase #7	$48.59	5.619%	$51.3203	$51.32	$51.30	$51.30
7 purchase totals =	$655.27		$716.2864	$716.29	$716.20	$716.30