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	$140.79	7.611%	$151.5055	$151.51	$151.50	$151.50
Purchase #2	$144.49	7.614%	$155.4915	$155.49	$155.50	$155.50
Purchase #3	$63.68	13.119%	$72.0342	$72.03	$72.05	$72.00
Purchase #4	$160.83	3.320%	$166.1696	$166.17	$166.15	$166.20
Purchase #5	$117.78	11.388%	$131.1928	$131.19	$131.20	$131.20
Purchase #6	$102.40	5.572%	$108.1057	$108.11	$108.10	$108.10
Purchase #7	$39.80	10.220%	$43.8676	$43.87	$43.85	$43.90
7 purchase totals =	$769.77		$828.3669	$828.37	$828.35	$828.40