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	$230.58	7.388%	$247.6153	$247.62	$247.60	$247.60
Purchase #2	$82.65	7.623%	$88.9504	$88.95	$88.95	$89.00
Purchase #3	$22.66	5.828%	$23.9806	$23.98	$24.00	$24.00
Purchase #4	$65.47	7.558%	$70.4182	$70.42	$70.40	$70.40
Purchase #5	$16.94	9.760%	$18.5933	$18.59	$18.60	$18.60
Purchase #6	$154.34	9.242%	$168.6041	$168.60	$168.60	$168.60
Purchase #7	$47.27	4.411%	$49.3551	$49.36	$49.35	$49.40
7 purchase totals =	$619.91		$667.5170	$667.52	$667.50	$667.60