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	$147.89	3.307%	$152.7807	$152.78	$152.80	$152.80
Purchase #2	$13.91	4.843%	$14.5837	$14.58	$14.60	$14.60
Purchase #3	$222.87	8.356%	$241.493	$241.49	$241.50	$241.50
Purchase #4	$186.62	7.584%	$200.7733	$200.77	$200.75	$200.80
Purchase #5	$218.31	7.566%	$234.8273	$234.83	$234.85	$234.80
Purchase #6	$86.92	6.649%	$92.6993	$92.70	$92.70	$92.70
Purchase #7	$33.81	13.411%	$38.3443	$38.34	$38.35	$38.30
7 purchase totals =	$910.33		$975.5016	$975.49	$975.55	$975.50