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	$78.92	9.549%	$86.4561	$86.46	$86.45	$86.50
Purchase #2	$49.43	5.816%	$52.3048	$52.30	$52.30	$52.30
Purchase #3	$142.33	4.285%	$148.4288	$148.43	$148.45	$148.40
Purchase #4	$37.26	4.137%	$38.8014	$38.80	$38.80	$38.80
Purchase #5	$184.60	13.873%	$210.2096	$210.21	$210.20	$210.20
Purchase #6	$5.74	3.332%	$5.9313	$5.93	$5.95	$5.90
Purchase #7	$130.61	5.602%	$137.9268	$137.93	$137.95	$137.90
7 purchase totals =	$628.89		$680.0588	$680.06	$680.10	$680.00