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	$244.36	7.658%	$263.0731	$263.07	$263.05	$263.10
Purchase #2	$104.46	6.141%	$110.8749	$110.87	$110.85	$110.90
Purchase #3	$63.72	4.824%	$66.7939	$66.79	$66.80	$66.80
Purchase #4	$82.59	10.284%	$91.0836	$91.08	$91.10	$91.10
Purchase #5	$219.86	6.341%	$233.8013	$233.80	$233.80	$233.80
Purchase #6	$118.41	4.218%	$123.4045	$123.40	$123.40	$123.40
Purchase #7	$68.32	3.219%	$70.5192	$70.52	$70.50	$70.50
7 purchase totals =	$901.72		$959.5505	$959.53	$959.50	$959.60