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	$127.36	9.609%	$139.598	$139.60	$139.60	$139.60
Purchase #2	$244.61	7.783%	$263.648	$263.65	$263.65	$263.60
Purchase #3	$143.78	8.602%	$156.148	$156.15	$156.15	$156.10
Purchase #4	$73.37	4.855%	$76.9321	$76.93	$76.95	$76.90
Purchase #5	$39.37	9.602%	$43.1503	$43.15	$43.15	$43.20
Purchase #6	$114.55	7.620%	$123.2787	$123.28	$123.30	$123.30
Purchase #7	$20.39	13.486%	$23.1398	$23.14	$23.15	$23.10
7 purchase totals =	$763.43		$825.8949	$825.90	$825.95	$825.80