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	$172.52	11.161%	$191.775	$191.78	$191.80	$191.80
Purchase #2	$92.25	11.455%	$102.8172	$102.82	$102.80	$102.80
Purchase #3	$66.71	13.396%	$75.6465	$75.65	$75.65	$75.60
Purchase #4	$164.79	5.329%	$173.5717	$173.57	$173.55	$173.60
Purchase #5	$54.99	8.365%	$59.5899	$59.59	$59.60	$59.60
Purchase #6	$249.55	12.141%	$279.8479	$279.85	$279.85	$279.80
Purchase #7	$137.34	7.685%	$147.8946	$147.89	$147.90	$147.90
7 purchase totals =	$938.15		$1,031.1428	$1,031.15	$1,031.15	$1,031.10