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	$141.70	9.723%	$155.4775	$155.48	$155.50	$155.50
Purchase #2	$204.34	11.315%	$227.4611	$227.46	$227.45	$227.50
Purchase #3	$164.66	4.549%	$172.1504	$172.15	$172.15	$172.20
Purchase #4	$131.66	8.348%	$142.651	$142.65	$142.65	$142.70
Purchase #5	$127.27	12.594%	$143.2984	$143.30	$143.30	$143.30
Purchase #6	$164.44	3.174%	$169.6593	$169.66	$169.65	$169.70
Purchase #7	$9.48	11.622%	$10.5818	$10.58	$10.60	$10.60
7 purchase totals =	$943.55		$1,021.2795	$1,021.28	$1,021.30	$1,021.50