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	$117.64	4.684%	$123.1503	$123.15	$123.15	$123.20
Purchase #2	$199.82	7.849%	$215.5039	$215.50	$215.50	$215.50
Purchase #3	$153.25	5.413%	$161.5454	$161.55	$161.55	$161.50
Purchase #4	$112.31	13.867%	$127.884	$127.88	$127.90	$127.90
Purchase #5	$51.44	5.627%	$54.3345	$54.33	$54.35	$54.30
Purchase #6	$108.46	11.125%	$120.5262	$120.53	$120.55	$120.50
Purchase #7	$200.93	11.675%	$224.3886	$224.39	$224.40	$224.40
7 purchase totals =	$943.85		$1,027.3329	$1,027.33	$1,027.40	$1,027.30