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	$103.96	7.360%	$111.6115	$111.61	$111.60	$111.60
Purchase #2	$246.89	7.724%	$265.9598	$265.96	$265.95	$266.00
Purchase #3	$151.76	13.853%	$172.7833	$172.78	$172.80	$172.80
Purchase #4	$195.76	10.348%	$216.0172	$216.02	$216.00	$216.00
Purchase #5	$61.68	13.691%	$70.1246	$70.12	$70.10	$70.10
Purchase #6	$246.45	4.249%	$256.9217	$256.92	$256.90	$256.90
Purchase #7	$179.75	11.273%	$200.0132	$200.01	$200.00	$200.00
7 purchase totals =	$1,186.25		$1,293.4313	$1,293.42	$1,293.35	$1,293.40