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	$203.37	4.129%	$211.7671	$211.77	$211.75	$211.80
Purchase #2	$143.41	7.547%	$154.2332	$154.23	$154.25	$154.20
Purchase #3	$145.46	8.711%	$158.131	$158.13	$158.15	$158.10
Purchase #4	$92.99	11.172%	$103.3788	$103.38	$103.40	$103.40
Purchase #5	$101.38	13.491%	$115.0572	$115.06	$115.05	$115.10
Purchase #6	$93.83	7.484%	$100.8522	$100.85	$100.85	$100.90
Purchase #7	$179.78	10.788%	$199.1747	$199.17	$199.15	$199.20
7 purchase totals =	$960.22		$1,042.5942	$1,042.59	$1,042.60	$1,042.70