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	$237.40	8.773%	$258.2271	$258.23	$258.25	$258.20
Purchase #2	$99.78	7.161%	$106.9252	$106.93	$106.95	$106.90
Purchase #3	$25.35	13.565%	$28.7887	$28.79	$28.80	$28.80
Purchase #4	$227.56	8.365%	$246.5954	$246.60	$246.60	$246.60
Purchase #5	$133.68	5.763%	$141.384	$141.38	$141.40	$141.40
Purchase #6	$139.42	10.858%	$154.5582	$154.56	$154.55	$154.60
Purchase #7	$119.64	6.447%	$127.3532	$127.35	$127.35	$127.40
7 purchase totals =	$982.83		$1,063.8318	$1,063.84	$1,063.90	$1,063.90