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	$108.71	13.685%	$123.587	$123.59	$123.60	$123.60
Purchase #2	$61.80	6.146%	$65.5982	$65.60	$65.60	$65.60
Purchase #3	$26.95	11.640%	$30.087	$30.09	$30.10	$30.10
Purchase #4	$41.90	12.333%	$47.0675	$47.07	$47.05	$47.10
Purchase #5	$249.96	3.664%	$259.1185	$259.12	$259.10	$259.10
Purchase #6	$104.79	9.264%	$114.4977	$114.50	$114.50	$114.50
Purchase #7	$153.35	7.130%	$164.2839	$164.28	$164.30	$164.30
7 purchase totals =	$747.46		$804.2398	$804.25	$804.25	$804.30