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	$125.65	13.609%	$142.7497	$142.75	$142.75	$142.70
Purchase #2	$86.65	6.707%	$92.4616	$92.46	$92.45	$92.50
Purchase #3	$48.86	11.110%	$54.2883	$54.29	$54.30	$54.30
Purchase #4	$86.38	11.182%	$96.039	$96.04	$96.05	$96.00
Purchase #5	$136.82	10.693%	$151.4502	$151.45	$151.45	$151.50
Purchase #6	$15.28	11.534%	$17.0424	$17.04	$17.05	$17.00
Purchase #7	$175.27	13.799%	$199.4555	$199.46	$199.45	$199.50
7 purchase totals =	$674.91		$753.4867	$753.49	$753.50	$753.50