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	$154.77	11.295%	$172.2513	$172.25	$172.25	$172.30
Purchase #2	$87.94	13.841%	$100.1118	$100.11	$100.10	$100.10
Purchase #3	$99.69	5.856%	$105.5278	$105.53	$105.55	$105.50
Purchase #4	$162.75	3.478%	$168.4104	$168.41	$168.40	$168.40
Purchase #5	$157.45	7.215%	$168.81	$168.81	$168.80	$168.80
Purchase #6	$141.38	13.506%	$160.4748	$160.47	$160.45	$160.50
Purchase #7	$160.85	9.495%	$176.1227	$176.12	$176.10	$176.10
7 purchase totals =	$964.83		$1,051.7088	$1,051.70	$1,051.65	$1,051.70