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	$142.68	7.129%	$152.8517	$152.85	$152.85	$152.90
Purchase #2	$44.77	3.450%	$46.3146	$46.31	$46.30	$46.30
Purchase #3	$122.53	12.439%	$137.7715	$137.77	$137.75	$137.80
Purchase #4	$70.46	9.346%	$77.0452	$77.05	$77.05	$77.00
Purchase #5	$219.83	8.626%	$238.7925	$238.79	$238.80	$238.80
Purchase #6	$178.29	10.456%	$196.932	$196.93	$196.95	$196.90
Purchase #7	$98.64	4.296%	$102.8776	$102.88	$102.90	$102.90
7 purchase totals =	$877.20		$952.5851	$952.58	$952.60	$952.60