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	$52.95	3.404%	$54.7524	$54.75	$54.75	$54.80
Purchase #2	$65.28	10.636%	$72.2232	$72.22	$72.20	$72.20
Purchase #3	$124.70	11.647%	$139.2238	$139.22	$139.20	$139.20
Purchase #4	$24.59	5.480%	$25.9375	$25.94	$25.95	$25.90
Purchase #5	$29.49	13.625%	$33.508	$33.51	$33.50	$33.50
Purchase #6	$26.40	9.397%	$28.8808	$28.88	$28.90	$28.90
Purchase #7	$226.47	8.865%	$246.5466	$246.55	$246.55	$246.50
7 purchase totals =	$549.88		$601.0723	$601.07	$601.05	$601.00