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	$63.62	13.751%	$72.3684	$72.37	$72.35	$72.40
Purchase #2	$182.84	4.619%	$191.2854	$191.29	$191.30	$191.30
Purchase #3	$77.97	12.172%	$87.4605	$87.46	$87.45	$87.50
Purchase #4	$97.47	12.270%	$109.4296	$109.43	$109.45	$109.40
Purchase #5	$127.82	12.707%	$144.0621	$144.06	$144.05	$144.10
Purchase #6	$210.28	9.697%	$230.6709	$230.67	$230.65	$230.70
Purchase #7	$101.35	8.328%	$109.7904	$109.79	$109.80	$109.80
7 purchase totals =	$861.35		$945.0673	$945.07	$945.05	$945.20