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	$196.26	13.870%	$223.4813	$223.48	$223.50	$223.50
Purchase #2	$127.88	10.720%	$141.5887	$141.59	$141.60	$141.60
Purchase #3	$109.48	4.856%	$114.7963	$114.80	$114.80	$114.80
Purchase #4	$31.26	5.504%	$32.9806	$32.98	$33.00	$33.00
Purchase #5	$227.46	12.205%	$255.2215	$255.22	$255.20	$255.20
Purchase #6	$24.45	12.475%	$27.5001	$27.50	$27.50	$27.50
Purchase #7	$65.52	9.188%	$71.54	$71.54	$71.55	$71.50
7 purchase totals =	$782.31		$867.1085	$867.11	$867.15	$867.10