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	$67.87	6.326%	$72.1635	$72.16	$72.15	$72.20
Purchase #2	$187.85	4.557%	$196.4103	$196.41	$196.40	$196.40
Purchase #3	$21.84	3.748%	$22.6586	$22.66	$22.65	$22.70
Purchase #4	$49.48	7.549%	$53.2152	$53.22	$53.20	$53.20
Purchase #5	$77.47	4.587%	$81.0235	$81.02	$81.00	$81.00
Purchase #6	$122.66	9.666%	$134.5163	$134.52	$134.50	$134.50
Purchase #7	$137.40	5.321%	$144.7111	$144.71	$144.70	$144.70
7 purchase totals =	$664.57		$704.6985	$704.70	$704.60	$704.70