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	$106.48	6.696%	$113.6099	$113.61	$113.60	$113.60
Purchase #2	$158.88	13.595%	$180.4797	$180.48	$180.50	$180.50
Purchase #3	$145.77	5.187%	$153.3311	$153.33	$153.35	$153.30
Purchase #4	$246.70	6.476%	$262.6763	$262.68	$262.70	$262.70
Purchase #5	$68.95	4.664%	$72.1658	$72.17	$72.15	$72.20
Purchase #6	$132.51	12.821%	$149.4991	$149.50	$149.50	$149.50
Purchase #7	$218.40	10.267%	$240.8231	$240.82	$240.80	$240.80
7 purchase totals =	$1,077.69		$1,172.5850	$1,172.59	$1,172.60	$1,172.60