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	$14.89	3.171%	$15.3622	$15.36	$15.35	$15.40
Purchase #2	$37.47	10.750%	$41.498	$41.50	$41.50	$41.50
Purchase #3	$40.64	4.842%	$42.6078	$42.61	$42.60	$42.60
Purchase #4	$240.73	6.630%	$256.6904	$256.69	$256.70	$256.70
Purchase #5	$36.28	13.123%	$41.041	$41.04	$41.05	$41.00
Purchase #6	$230.81	9.347%	$252.3838	$252.38	$252.40	$252.40
Purchase #7	$45.59	7.717%	$49.1082	$49.11	$49.10	$49.10
7 purchase totals =	$646.41		$698.6914	$698.69	$698.70	$698.70