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	$151.25	8.534%	$164.1577	$164.16	$164.15	$164.20
Purchase #2	$39.40	10.524%	$43.5465	$43.55	$43.55	$43.50
Purchase #3	$59.50	11.840%	$66.5448	$66.54	$66.55	$66.50
Purchase #4	$105.70	3.852%	$109.7716	$109.77	$109.75	$109.80
Purchase #5	$50.80	12.319%	$57.0581	$57.06	$57.05	$57.10
Purchase #6	$116.77	6.712%	$124.6076	$124.61	$124.60	$124.60
Purchase #7	$127.39	8.353%	$138.0309	$138.03	$138.05	$138.00
7 purchase totals =	$650.81		$703.7172	$703.72	$703.70	$703.70