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	$113.58	12.836%	$128.1591	$128.16	$128.15	$128.20
Purchase #2	$49.29	10.567%	$54.4985	$54.50	$54.50	$54.50
Purchase #3	$174.72	11.483%	$194.7831	$194.78	$194.80	$194.80
Purchase #4	$38.70	7.577%	$41.6323	$41.63	$41.65	$41.60
Purchase #5	$153.74	12.150%	$172.4194	$172.42	$172.40	$172.40
Purchase #6	$205.40	11.233%	$228.4726	$228.47	$228.45	$228.50
Purchase #7	$9.90	3.376%	$10.2342	$10.23	$10.25	$10.20
7 purchase totals =	$745.33		$830.1992	$830.19	$830.20	$830.20