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	$212.82	11.475%	$237.2411	$237.24	$237.25	$237.20
Purchase #2	$82.95	8.563%	$90.053	$90.05	$90.05	$90.10
Purchase #3	$117.88	9.280%	$128.8193	$128.82	$128.80	$128.80
Purchase #4	$129.43	11.509%	$144.3261	$144.33	$144.35	$144.30
Purchase #5	$174.92	9.703%	$191.8925	$191.89	$191.90	$191.90
Purchase #6	$108.72	6.435%	$115.7161	$115.72	$115.70	$115.70
Purchase #7	$41.52	3.761%	$43.0816	$43.08	$43.10	$43.10
7 purchase totals =	$868.24		$951.1297	$951.13	$951.15	$951.10