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	$137.86	10.838%	$152.8013	$152.80	$152.80	$152.80
Purchase #2	$197.64	4.553%	$206.6385	$206.64	$206.65	$206.60
Purchase #3	$67.49	3.131%	$69.6031	$69.60	$69.60	$69.60
Purchase #4	$183.53	13.648%	$208.5782	$208.58	$208.60	$208.60
Purchase #5	$220.54	13.185%	$249.6182	$249.62	$249.60	$249.60
Purchase #6	$115.35	10.260%	$127.1849	$127.18	$127.20	$127.20
Purchase #7	$58.97	13.406%	$66.8755	$66.88	$66.90	$66.90
7 purchase totals =	$981.38		$1,081.2997	$1,081.30	$1,081.35	$1,081.30