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	$23.70	7.640%	$25.5107	$25.51	$25.50	$25.50
Purchase #2	$59.74	3.491%	$61.8255	$61.83	$61.85	$61.80
Purchase #3	$213.50	5.328%	$224.8753	$224.88	$224.90	$224.90
Purchase #4	$112.80	13.102%	$127.5791	$127.58	$127.60	$127.60
Purchase #5	$180.54	8.633%	$196.126	$196.13	$196.15	$196.10
Purchase #6	$16.64	5.233%	$17.5108	$17.51	$17.50	$17.50
Purchase #7	$90.65	5.128%	$95.2985	$95.30	$95.30	$95.30
7 purchase totals =	$697.57		$748.7259	$748.74	$748.80	$748.70