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	$40.80	9.745%	$44.776	$44.78	$44.80	$44.80
Purchase #2	$17.60	5.830%	$18.6261	$18.63	$18.65	$18.60
Purchase #3	$213.58	13.161%	$241.6893	$241.69	$241.70	$241.70
Purchase #4	$29.47	10.784%	$32.648	$32.65	$32.65	$32.60
Purchase #5	$184.32	6.784%	$196.8243	$196.82	$196.80	$196.80
Purchase #6	$171.80	8.417%	$186.2604	$186.26	$186.25	$186.30
Purchase #7	$157.89	5.373%	$166.3734	$166.37	$166.35	$166.40
7 purchase totals =	$815.46		$887.1975	$887.20	$887.20	$887.20