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	$82.79	7.725%	$89.1855	$89.19	$89.20	$89.20
Purchase #2	$125.85	9.264%	$137.5087	$137.51	$137.50	$137.50
Purchase #3	$199.99	4.311%	$208.6116	$208.61	$208.60	$208.60
Purchase #4	$67.42	6.801%	$72.0052	$72.01	$72.00	$72.00
Purchase #5	$149.59	5.848%	$158.338	$158.34	$158.35	$158.30
Purchase #6	$172.27	9.660%	$188.9113	$188.91	$188.90	$188.90
Purchase #7	$69.51	7.642%	$74.822	$74.82	$74.80	$74.80
7 purchase totals =	$867.42		$929.3823	$929.39	$929.35	$929.30