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	$106.89	5.149%	$112.3938	$112.39	$112.40	$112.40
Purchase #2	$134.56	7.536%	$144.7004	$144.70	$144.70	$144.70
Purchase #3	$146.25	12.532%	$164.5781	$164.58	$164.60	$164.60
Purchase #4	$186.87	12.292%	$209.8401	$209.84	$209.85	$209.80
Purchase #5	$112.37	6.606%	$119.7932	$119.79	$119.80	$119.80
Purchase #6	$62.43	7.630%	$67.1934	$67.19	$67.20	$67.20
Purchase #7	$63.52	3.191%	$65.5469	$65.55	$65.55	$65.50
7 purchase totals =	$812.89		$884.0459	$884.04	$884.10	$884.00