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	$98.42	4.874%	$103.217	$103.22	$103.20	$103.20
Purchase #2	$18.84	7.599%	$20.2717	$20.27	$20.25	$20.30
Purchase #3	$233.90	5.391%	$246.5095	$246.51	$246.50	$246.50
Purchase #4	$122.25	8.632%	$132.8026	$132.80	$132.80	$132.80
Purchase #5	$37.60	6.689%	$40.1151	$40.12	$40.10	$40.10
Purchase #6	$36.38	10.381%	$40.1566	$40.16	$40.15	$40.20
Purchase #7	$230.57	6.225%	$244.923	$244.92	$244.90	$244.90
7 purchase totals =	$777.96		$827.9955	$828.00	$827.90	$828.00