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	$110.32	7.414%	$118.4991	$118.50	$118.50	$118.50
Purchase #2	$95.38	10.315%	$105.2184	$105.22	$105.20	$105.20
Purchase #3	$21.83	13.391%	$24.7533	$24.75	$24.75	$24.80
Purchase #4	$179.42	9.415%	$196.3124	$196.31	$196.30	$196.30
Purchase #5	$113.97	8.448%	$123.5982	$123.60	$123.60	$123.60
Purchase #6	$214.97	6.103%	$228.0896	$228.09	$228.10	$228.10
Purchase #7	$140.66	13.796%	$160.0655	$160.07	$160.05	$160.10
7 purchase totals =	$876.55		$956.5365	$956.54	$956.50	$956.60