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	$41.97	8.175%	$45.401	$45.40	$45.40	$45.40
Purchase #2	$54.35	12.864%	$61.3416	$61.34	$61.35	$61.30
Purchase #3	$208.99	3.473%	$216.2482	$216.25	$216.25	$216.20
Purchase #4	$10.88	13.471%	$12.3456	$12.35	$12.35	$12.30
Purchase #5	$9.77	8.641%	$10.6142	$10.61	$10.60	$10.60
Purchase #6	$18.39	6.509%	$19.587	$19.59	$19.60	$19.60
Purchase #7	$53.81	9.437%	$58.888	$58.89	$58.90	$58.90
7 purchase totals =	$398.16		$424.4256	$424.43	$424.45	$424.30