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	$72.88	10.231%	$80.3364	$80.34	$80.35	$80.30
Purchase #2	$132.92	3.730%	$137.8779	$137.88	$137.90	$137.90
Purchase #3	$75.29	8.361%	$81.585	$81.59	$81.60	$81.60
Purchase #4	$117.85	8.211%	$127.5267	$127.53	$127.55	$127.50
Purchase #5	$248.34	13.461%	$281.769	$281.77	$281.75	$281.80
Purchase #6	$201.38	8.866%	$219.2344	$219.23	$219.25	$219.20
Purchase #7	$86.82	10.419%	$95.8658	$95.87	$95.85	$95.90
7 purchase totals =	$935.48		$1,024.1952	$1,024.21	$1,024.25	$1,024.20