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	$37.96	11.709%	$42.4047	$42.40	$42.40	$42.40
Purchase #2	$36.96	11.298%	$41.1357	$41.14	$41.15	$41.10
Purchase #3	$127.46	6.773%	$136.0929	$136.09	$136.10	$136.10
Purchase #4	$84.38	6.768%	$90.0908	$90.09	$90.10	$90.10
Purchase #5	$183.45	11.298%	$204.1762	$204.18	$204.20	$204.20
Purchase #6	$53.99	8.422%	$58.537	$58.54	$58.55	$58.50
Purchase #7	$141.28	11.553%	$157.6021	$157.60	$157.60	$157.60
7 purchase totals =	$665.48		$730.0394	$730.04	$730.10	$730.00