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	$56.66	8.690%	$61.5838	$61.58	$61.60	$61.60
Purchase #2	$146.78	8.202%	$158.8189	$158.82	$158.80	$158.80
Purchase #3	$250.67	3.774%	$260.1303	$260.13	$260.15	$260.10
Purchase #4	$90.58	12.438%	$101.8463	$101.85	$101.85	$101.80
Purchase #5	$99.96	5.636%	$105.5937	$105.59	$105.60	$105.60
Purchase #6	$38.27	4.400%	$39.9539	$39.95	$39.95	$40.00
Purchase #7	$91.82	8.747%	$99.8515	$99.85	$99.85	$99.90
7 purchase totals =	$774.74		$827.7784	$827.77	$827.80	$827.80