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	$141.33	7.378%	$151.7573	$151.76	$151.75	$151.80
Purchase #2	$217.51	3.635%	$225.4165	$225.42	$225.40	$225.40
Purchase #3	$241.47	12.866%	$272.5375	$272.54	$272.55	$272.50
Purchase #4	$153.40	11.817%	$171.5273	$171.53	$171.55	$171.50
Purchase #5	$42.88	6.784%	$45.789	$45.79	$45.80	$45.80
Purchase #6	$148.87	10.660%	$164.7395	$164.74	$164.75	$164.70
Purchase #7	$249.83	13.574%	$283.7419	$283.74	$283.75	$283.70
7 purchase totals =	$1,195.29		$1,315.5090	$1,315.52	$1,315.55	$1,315.40