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	$60.34	10.431%	$66.6341	$66.63	$66.65	$66.60
Purchase #2	$165.82	9.320%	$181.2744	$181.27	$181.25	$181.30
Purchase #3	$213.98	4.125%	$222.8067	$222.81	$222.80	$222.80
Purchase #4	$231.72	5.476%	$244.409	$244.41	$244.40	$244.40
Purchase #5	$55.60	10.773%	$61.5898	$61.59	$61.60	$61.60
Purchase #6	$19.49	8.869%	$21.2186	$21.22	$21.20	$21.20
Purchase #7	$81.90	5.210%	$86.167	$86.17	$86.15	$86.20
7 purchase totals =	$828.85		$884.0996	$884.10	$884.05	$884.10