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	$107.85	4.476%	$112.6774	$112.68	$112.70	$112.70
Purchase #2	$29.67	12.208%	$33.2921	$33.29	$33.30	$33.30
Purchase #3	$143.92	13.536%	$163.401	$163.40	$163.40	$163.40
Purchase #4	$43.92	4.238%	$45.7813	$45.78	$45.80	$45.80
Purchase #5	$165.26	12.706%	$186.2579	$186.26	$186.25	$186.30
Purchase #6	$89.59	6.182%	$95.1285	$95.13	$95.15	$95.10
Purchase #7	$29.38	4.463%	$30.6912	$30.69	$30.70	$30.70
7 purchase totals =	$609.59		$667.2294	$667.23	$667.30	$667.30