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	$151.29	13.240%	$171.3208	$171.32	$171.30	$171.30
Purchase #2	$202.94	8.674%	$220.543	$220.54	$220.55	$220.50
Purchase #3	$101.99	9.440%	$111.6179	$111.62	$111.60	$111.60
Purchase #4	$127.32	12.693%	$143.4807	$143.48	$143.50	$143.50
Purchase #5	$155.40	6.405%	$165.3534	$165.35	$165.35	$165.40
Purchase #6	$227.54	12.516%	$256.0189	$256.02	$256.00	$256.00
Purchase #7	$95.52	8.184%	$103.3374	$103.34	$103.35	$103.30
7 purchase totals =	$1,062.00		$1,171.6721	$1,171.67	$1,171.65	$1,171.60