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	$175.41	8.395%	$190.1357	$190.14	$190.15	$190.10
Purchase #2	$37.67	13.159%	$42.627	$42.63	$42.65	$42.60
Purchase #3	$156.25	13.189%	$176.8578	$176.86	$176.85	$176.90
Purchase #4	$241.55	5.307%	$254.3691	$254.37	$254.35	$254.40
Purchase #5	$195.85	13.584%	$222.4543	$222.45	$222.45	$222.50
Purchase #6	$144.92	10.610%	$160.296	$160.30	$160.30	$160.30
Purchase #7	$90.98	3.672%	$94.3208	$94.32	$94.30	$94.30
7 purchase totals =	$1,042.63		$1,141.0607	$1,141.07	$1,141.05	$1,141.10