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	$218.58	10.540%	$241.6183	$241.62	$241.60	$241.60
Purchase #2	$62.54	13.176%	$70.7803	$70.78	$70.80	$70.80
Purchase #3	$26.72	3.465%	$27.6458	$27.65	$27.65	$27.60
Purchase #4	$82.98	12.584%	$93.4222	$93.42	$93.40	$93.40
Purchase #5	$78.59	13.822%	$89.4527	$89.45	$89.45	$89.50
Purchase #6	$199.41	10.826%	$220.9981	$221.00	$221.00	$221.00
Purchase #7	$46.90	13.157%	$53.0706	$53.07	$53.05	$53.10
7 purchase totals =	$715.72		$796.9880	$796.99	$796.95	$797.00