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	$174.81	3.632%	$181.1591	$181.16	$181.15	$181.20
Purchase #2	$204.69	7.545%	$220.1339	$220.13	$220.15	$220.10
Purchase #3	$185.83	10.609%	$205.5447	$205.54	$205.55	$205.50
Purchase #4	$237.63	12.152%	$266.5068	$266.51	$266.50	$266.50
Purchase #5	$136.92	3.571%	$141.8094	$141.81	$141.80	$141.80
Purchase #6	$92.83	13.447%	$105.3129	$105.31	$105.30	$105.30
Purchase #7	$118.30	12.728%	$133.3572	$133.36	$133.35	$133.40
7 purchase totals =	$1,151.01		$1,253.8240	$1,253.82	$1,253.80	$1,253.80