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	$51.91	8.141%	$56.136	$56.14	$56.15	$56.10
Purchase #2	$67.41	6.340%	$71.6838	$71.68	$71.70	$71.70
Purchase #3	$95.82	10.872%	$106.2376	$106.24	$106.25	$106.20
Purchase #4	$41.99	11.622%	$46.8701	$46.87	$46.85	$46.90
Purchase #5	$166.59	11.336%	$185.4746	$185.47	$185.45	$185.50
Purchase #6	$43.82	4.481%	$45.7836	$45.78	$45.80	$45.80
Purchase #7	$93.47	9.823%	$102.6516	$102.65	$102.65	$102.70
7 purchase totals =	$561.01		$614.8373	$614.83	$614.85	$614.90