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	$206.74	6.703%	$220.5978	$220.60	$220.60	$220.60
Purchase #2	$160.81	4.267%	$167.6718	$167.67	$167.65	$167.70
Purchase #3	$34.87	7.240%	$37.3946	$37.39	$37.40	$37.40
Purchase #4	$248.51	3.141%	$256.3157	$256.32	$256.30	$256.30
Purchase #5	$250.51	12.463%	$281.7311	$281.73	$281.75	$281.70
Purchase #6	$53.26	12.126%	$59.7183	$59.72	$59.70	$59.70
Purchase #7	$225.36	13.171%	$255.0422	$255.04	$255.05	$255.00
7 purchase totals =	$1,180.06		$1,278.4715	$1,278.47	$1,278.45	$1,278.40