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	$54.84	8.154%	$59.3117	$59.31	$59.30	$59.30
Purchase #2	$63.70	4.690%	$66.6875	$66.69	$66.70	$66.70
Purchase #3	$171.78	6.308%	$182.6159	$182.62	$182.60	$182.60
Purchase #4	$224.38	8.510%	$243.4747	$243.47	$243.45	$243.50
Purchase #5	$16.47	11.252%	$18.3232	$18.32	$18.30	$18.30
Purchase #6	$14.25	6.109%	$15.1205	$15.12	$15.10	$15.10
Purchase #7	$125.53	8.692%	$136.4411	$136.44	$136.45	$136.40
7 purchase totals =	$670.95		$721.9746	$721.97	$721.90	$721.90