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	$58.37	13.180%	$66.0632	$66.06	$66.05	$66.10
Purchase #2	$69.61	13.126%	$78.747	$78.75	$78.75	$78.70
Purchase #3	$107.44	11.776%	$120.0921	$120.09	$120.10	$120.10
Purchase #4	$61.47	9.198%	$67.124	$67.12	$67.10	$67.10
Purchase #5	$83.39	13.739%	$94.847	$94.85	$94.85	$94.80
Purchase #6	$213.38	11.346%	$237.5901	$237.59	$237.60	$237.60
Purchase #7	$46.27	3.572%	$47.9228	$47.92	$47.90	$47.90
7 purchase totals =	$639.93		$712.3862	$712.38	$712.35	$712.30