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	$211.94	3.547%	$219.4575	$219.46	$219.45	$219.50
Purchase #2	$80.67	3.631%	$83.5991	$83.60	$83.60	$83.60
Purchase #3	$44.65	11.677%	$49.8638	$49.86	$49.85	$49.90
Purchase #4	$194.70	11.484%	$217.0593	$217.06	$217.05	$217.10
Purchase #5	$10.47	4.360%	$10.9265	$10.93	$10.95	$10.90
Purchase #6	$153.47	9.621%	$168.2353	$168.24	$168.25	$168.20
Purchase #7	$134.99	12.262%	$151.5425	$151.54	$151.55	$151.50
7 purchase totals =	$830.89		$900.6840	$900.69	$900.70	$900.70