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	$167.86	13.342%	$190.2559	$190.26	$190.25	$190.30
Purchase #2	$146.37	6.798%	$156.3202	$156.32	$156.30	$156.30
Purchase #3	$226.89	9.622%	$248.7214	$248.72	$248.70	$248.70
Purchase #4	$96.85	5.452%	$102.1303	$102.13	$102.15	$102.10
Purchase #5	$164.72	13.269%	$186.5767	$186.58	$186.60	$186.60
Purchase #6	$193.66	10.738%	$214.4552	$214.46	$214.45	$214.50
Purchase #7	$7.46	4.603%	$7.8034	$7.80	$7.80	$7.80
7 purchase totals =	$1,003.81		$1,106.2631	$1,106.27	$1,106.25	$1,106.30