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	$157.25	8.756%	$171.0188	$171.02	$171.00	$171.00
Purchase #2	$138.45	10.234%	$152.619	$152.62	$152.60	$152.60
Purchase #3	$58.56	5.126%	$61.5618	$61.56	$61.55	$61.60
Purchase #4	$153.70	3.218%	$158.6461	$158.65	$158.65	$158.60
Purchase #5	$164.48	4.622%	$172.0823	$172.08	$172.10	$172.10
Purchase #6	$168.28	5.112%	$176.8825	$176.88	$176.90	$176.90
Purchase #7	$220.75	4.792%	$231.3283	$231.33	$231.35	$231.30
7 purchase totals =	$1,061.47		$1,124.1388	$1,124.14	$1,124.15	$1,124.10