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	$35.47	4.780%	$37.1655	$37.17	$37.15	$37.20
Purchase #2	$48.29	6.358%	$51.3603	$51.36	$51.35	$51.40
Purchase #3	$23.25	4.277%	$24.2444	$24.24	$24.25	$24.20
Purchase #4	$138.68	11.215%	$154.233	$154.23	$154.25	$154.20
Purchase #5	$111.58	13.380%	$126.5094	$126.51	$126.50	$126.50
Purchase #6	$37.48	5.393%	$39.5013	$39.50	$39.50	$39.50
Purchase #7	$36.53	4.754%	$38.2666	$38.27	$38.25	$38.30
7 purchase totals =	$431.28		$471.2805	$471.28	$471.25	$471.30