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	$41.98	4.811%	$43.9997	$44.00	$44.00	$44.00
Purchase #2	$145.69	10.428%	$160.8826	$160.88	$160.90	$160.90
Purchase #3	$94.43	6.661%	$100.72	$100.72	$100.70	$100.70
Purchase #4	$25.91	10.321%	$28.5842	$28.58	$28.60	$28.60
Purchase #5	$36.53	3.173%	$37.6891	$37.69	$37.70	$37.70
Purchase #6	$104.92	8.509%	$113.8476	$113.85	$113.85	$113.80
Purchase #7	$217.75	9.642%	$238.7455	$238.75	$238.75	$238.70
7 purchase totals =	$667.21		$724.4687	$724.47	$724.50	$724.40