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	$32.40	7.257%	$34.7513	$34.75	$34.75	$34.80
Purchase #2	$97.91	12.622%	$110.2682	$110.27	$110.25	$110.30
Purchase #3	$216.77	6.644%	$231.1722	$231.17	$231.15	$231.20
Purchase #4	$240.58	6.269%	$255.662	$255.66	$255.65	$255.70
Purchase #5	$180.80	5.321%	$190.4204	$190.42	$190.40	$190.40
Purchase #6	$145.33	4.246%	$151.5007	$151.50	$151.50	$151.50
Purchase #7	$144.30	6.357%	$153.4732	$153.47	$153.45	$153.50
7 purchase totals =	$1,058.09		$1,127.2480	$1,127.24	$1,127.15	$1,127.40