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	$119.76	6.835%	$127.9456	$127.95	$127.95	$127.90
Purchase #2	$98.65	4.837%	$103.4217	$103.42	$103.40	$103.40
Purchase #3	$217.81	7.350%	$233.819	$233.82	$233.80	$233.80
Purchase #4	$208.27	6.376%	$221.5493	$221.55	$221.55	$221.50
Purchase #5	$17.38	10.864%	$19.2682	$19.27	$19.25	$19.30
Purchase #6	$83.81	3.386%	$86.6478	$86.65	$86.65	$86.60
Purchase #7	$179.70	3.140%	$185.3426	$185.34	$185.35	$185.30
7 purchase totals =	$925.38		$977.9942	$978.00	$977.95	$977.80