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	$249.43	5.768%	$263.8171	$263.82	$263.80	$263.80
Purchase #2	$153.81	8.860%	$167.4376	$167.44	$167.45	$167.40
Purchase #3	$51.77	6.512%	$55.1413	$55.14	$55.15	$55.10
Purchase #4	$109.88	4.399%	$114.7136	$114.71	$114.70	$114.70
Purchase #5	$205.46	12.727%	$231.6089	$231.61	$231.60	$231.60
Purchase #6	$246.64	3.612%	$255.5486	$255.55	$255.55	$255.50
Purchase #7	$22.82	7.626%	$24.5603	$24.56	$24.55	$24.60
7 purchase totals =	$1,039.81		$1,112.8274	$1,112.83	$1,112.80	$1,112.70