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	$220.66	6.286%	$234.5307	$234.53	$234.55	$234.50
Purchase #2	$87.49	13.656%	$99.4376	$99.44	$99.45	$99.40
Purchase #3	$143.67	7.605%	$154.5961	$154.60	$154.60	$154.60
Purchase #4	$103.26	7.592%	$111.0995	$111.10	$111.10	$111.10
Purchase #5	$136.91	7.605%	$147.322	$147.32	$147.30	$147.30
Purchase #6	$107.48	4.397%	$112.2059	$112.21	$112.20	$112.20
Purchase #7	$79.80	8.103%	$86.2662	$86.27	$86.25	$86.30
7 purchase totals =	$879.27		$945.4580	$945.47	$945.45	$945.40