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	$207.32	5.439%	$218.5961	$218.60	$218.60	$218.60
Purchase #2	$81.95	12.281%	$92.0143	$92.01	$92.00	$92.00
Purchase #3	$166.43	12.359%	$186.9991	$187.00	$187.00	$187.00
Purchase #4	$218.43	5.305%	$230.0177	$230.02	$230.00	$230.00
Purchase #5	$41.47	10.208%	$45.7033	$45.70	$45.70	$45.70
Purchase #6	$93.82	10.684%	$103.8437	$103.84	$103.85	$103.80
Purchase #7	$133.98	5.629%	$141.5217	$141.52	$141.50	$141.50
7 purchase totals =	$943.40		$1,018.6959	$1,018.69	$1,018.65	$1,018.60