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	$94.64	12.549%	$106.5164	$106.52	$106.50	$106.50
Purchase #2	$190.65	3.265%	$196.8747	$196.87	$196.85	$196.90
Purchase #3	$62.38	5.645%	$65.9014	$65.90	$65.90	$65.90
Purchase #4	$142.41	7.592%	$153.2218	$153.22	$153.20	$153.20
Purchase #5	$52.31	10.721%	$57.9182	$57.92	$57.90	$57.90
Purchase #6	$12.72	11.769%	$14.217	$14.22	$14.20	$14.20
Purchase #7	$214.28	4.523%	$223.9719	$223.97	$223.95	$224.00
7 purchase totals =	$769.39		$818.6214	$818.62	$818.50	$818.60