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	$126.25	9.495%	$138.2374	$138.24	$138.25	$138.20
Purchase #2	$5.40	10.123%	$5.9466	$5.95	$5.95	$5.90
Purchase #3	$110.60	12.361%	$124.2713	$124.27	$124.25	$124.30
Purchase #4	$11.55	11.425%	$12.8696	$12.87	$12.85	$12.90
Purchase #5	$116.62	5.858%	$123.4516	$123.45	$123.45	$123.50
Purchase #6	$186.37	5.273%	$196.1973	$196.20	$196.20	$196.20
Purchase #7	$99.78	3.595%	$103.3671	$103.37	$103.35	$103.40
7 purchase totals =	$656.57		$704.3409	$704.35	$704.30	$704.40