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	$111.80	6.858%	$119.4672	$119.47	$119.45	$119.50
Purchase #2	$204.54	4.873%	$214.5072	$214.51	$214.50	$214.50
Purchase #3	$121.87	5.514%	$128.5899	$128.59	$128.60	$128.60
Purchase #4	$140.35	9.694%	$153.9555	$153.96	$153.95	$154.00
Purchase #5	$110.37	11.722%	$123.3076	$123.31	$123.30	$123.30
Purchase #6	$96.36	9.376%	$105.3947	$105.39	$105.40	$105.40
Purchase #7	$28.96	10.711%	$32.0619	$32.06	$32.05	$32.10
7 purchase totals =	$814.25		$877.2840	$877.29	$877.25	$877.40