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	$127.29	4.218%	$132.6591	$132.66	$132.65	$132.70
Purchase #2	$51.66	3.747%	$53.5957	$53.60	$53.60	$53.60
Purchase #3	$226.77	12.189%	$254.411	$254.41	$254.40	$254.40
Purchase #4	$132.83	13.791%	$151.1486	$151.15	$151.15	$151.10
Purchase #5	$245.28	4.586%	$256.5285	$256.53	$256.55	$256.50
Purchase #6	$70.31	11.669%	$78.5145	$78.51	$78.50	$78.50
Purchase #7	$103.80	3.542%	$107.4766	$107.48	$107.50	$107.50
7 purchase totals =	$957.94		$1,034.3340	$1,034.34	$1,034.35	$1,034.30