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	$61.52	4.863%	$64.5117	$64.51	$64.50	$64.50
Purchase #2	$83.72	3.780%	$86.8846	$86.88	$86.90	$86.90
Purchase #3	$91.54	6.636%	$97.6146	$97.61	$97.60	$97.60
Purchase #4	$146.47	3.193%	$151.1468	$151.15	$151.15	$151.10
Purchase #5	$242.57	4.109%	$252.5372	$252.54	$252.55	$252.50
Purchase #6	$227.47	13.697%	$258.6266	$258.63	$258.65	$258.60
Purchase #7	$153.25	9.690%	$168.0999	$168.10	$168.10	$168.10
7 purchase totals =	$1,006.54		$1,079.4214	$1,079.42	$1,079.45	$1,079.30