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	$87.47	11.294%	$97.3489	$97.35	$97.35	$97.30
Purchase #2	$77.75	10.786%	$86.1361	$86.14	$86.15	$86.10
Purchase #3	$131.77	12.219%	$147.871	$147.87	$147.85	$147.90
Purchase #4	$198.87	4.605%	$208.028	$208.03	$208.05	$208.00
Purchase #5	$70.90	11.248%	$78.8748	$78.87	$78.85	$78.90
Purchase #6	$175.83	5.363%	$185.2598	$185.26	$185.25	$185.30
Purchase #7	$21.68	13.643%	$24.6378	$24.64	$24.65	$24.60
7 purchase totals =	$764.27		$828.1564	$828.16	$828.15	$828.10