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	$216.75	5.420%	$228.4979	$228.50	$228.50	$228.50
Purchase #2	$51.58	7.462%	$55.4289	$55.43	$55.45	$55.40
Purchase #3	$114.57	7.844%	$123.5569	$123.56	$123.55	$123.60
Purchase #4	$91.77	12.577%	$103.3119	$103.31	$103.30	$103.30
Purchase #5	$82.29	8.844%	$89.5677	$89.57	$89.55	$89.60
Purchase #6	$71.40	3.869%	$74.1625	$74.16	$74.15	$74.20
Purchase #7	$214.64	9.296%	$234.5929	$234.59	$234.60	$234.60
7 purchase totals =	$843.00		$909.1187	$909.12	$909.10	$909.20