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	$82.61	10.722%	$91.4674	$91.47	$91.45	$91.50
Purchase #2	$132.67	13.504%	$150.5858	$150.59	$150.60	$150.60
Purchase #3	$104.40	7.489%	$112.2185	$112.22	$112.20	$112.20
Purchase #4	$92.42	11.614%	$103.1537	$103.15	$103.15	$103.20
Purchase #5	$234.64	9.321%	$256.5108	$256.51	$256.50	$256.50
Purchase #6	$247.79	10.405%	$273.5725	$273.57	$273.55	$273.60
Purchase #7	$249.29	4.537%	$260.6003	$260.60	$260.60	$260.60
7 purchase totals =	$1,143.82		$1,248.1090	$1,248.11	$1,248.05	$1,248.20