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	$15.35	3.871%	$15.9442	$15.94	$15.95	$15.90
Purchase #2	$231.54	10.863%	$256.6922	$256.69	$256.70	$256.70
Purchase #3	$31.64	8.867%	$34.4455	$34.45	$34.45	$34.40
Purchase #4	$107.33	11.122%	$119.2672	$119.27	$119.25	$119.30
Purchase #5	$166.36	8.526%	$180.5439	$180.54	$180.55	$180.50
Purchase #6	$92.47	13.637%	$105.0801	$105.08	$105.10	$105.10
Purchase #7	$108.25	5.623%	$114.3369	$114.34	$114.35	$114.30
7 purchase totals =	$752.94		$826.3100	$826.31	$826.35	$826.20