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	$75.75	13.570%	$86.0293	$86.03	$86.05	$86.00
Purchase #2	$49.26	8.679%	$53.5353	$53.54	$53.55	$53.50
Purchase #3	$95.83	4.384%	$100.0312	$100.03	$100.05	$100.00
Purchase #4	$208.27	4.113%	$216.8361	$216.84	$216.85	$216.80
Purchase #5	$137.88	10.651%	$152.5656	$152.57	$152.55	$152.60
Purchase #6	$24.58	13.187%	$27.8214	$27.82	$27.80	$27.80
Purchase #7	$137.69	13.651%	$156.4861	$156.49	$156.50	$156.50
7 purchase totals =	$729.26		$793.3050	$793.32	$793.35	$793.20