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	$202.30	12.169%	$226.9179	$226.92	$226.90	$226.90
Purchase #2	$89.84	10.383%	$99.1681	$99.17	$99.15	$99.20
Purchase #3	$87.44	13.580%	$99.3144	$99.31	$99.30	$99.30
Purchase #4	$101.31	8.433%	$109.8535	$109.85	$109.85	$109.90
Purchase #5	$43.79	4.558%	$45.7859	$45.79	$45.80	$45.80
Purchase #6	$140.47	11.368%	$156.4386	$156.44	$156.45	$156.40
Purchase #7	$210.25	3.244%	$217.0705	$217.07	$217.05	$217.10
7 purchase totals =	$875.40		$954.5489	$954.55	$954.50	$954.60