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	$85.75	11.201%	$95.3549	$95.35	$95.35	$95.40
Purchase #2	$50.69	3.200%	$52.3121	$52.31	$52.30	$52.30
Purchase #3	$22.38	8.381%	$24.2557	$24.26	$24.25	$24.30
Purchase #4	$193.92	13.111%	$219.3449	$219.34	$219.35	$219.30
Purchase #5	$15.82	8.821%	$17.2155	$17.22	$17.20	$17.20
Purchase #6	$139.54	13.552%	$158.4505	$158.45	$158.45	$158.50
Purchase #7	$120.78	8.870%	$131.4932	$131.49	$131.50	$131.50
7 purchase totals =	$628.88		$698.4268	$698.42	$698.40	$698.50