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	$227.91	8.218%	$246.6396	$246.64	$246.65	$246.60
Purchase #2	$31.54	13.739%	$35.8733	$35.87	$35.85	$35.90
Purchase #3	$200.39	12.199%	$224.8356	$224.84	$224.85	$224.80
Purchase #4	$130.38	6.760%	$139.1937	$139.19	$139.20	$139.20
Purchase #5	$187.69	9.486%	$205.4943	$205.49	$205.50	$205.50
Purchase #6	$249.58	10.420%	$275.5862	$275.59	$275.60	$275.60
Purchase #7	$27.28	4.226%	$28.4329	$28.43	$28.45	$28.40
7 purchase totals =	$1,054.77		$1,156.0556	$1,156.05	$1,156.10	$1,156.00