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	$146.86	7.797%	$158.3107	$158.31	$158.30	$158.30
Purchase #2	$97.29	7.391%	$104.4807	$104.48	$104.50	$104.50
Purchase #3	$147.41	4.112%	$153.4715	$153.47	$153.45	$153.50
Purchase #4	$214.88	5.575%	$226.8596	$226.86	$226.85	$226.90
Purchase #5	$6.44	13.446%	$7.3059	$7.31	$7.30	$7.30
Purchase #6	$25.42	8.857%	$27.6714	$27.67	$27.65	$27.70
Purchase #7	$97.82	10.740%	$108.3259	$108.33	$108.35	$108.30
7 purchase totals =	$736.12		$786.4257	$786.43	$786.40	$786.50