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	$62.37	8.540%	$67.6964	$67.70	$67.70	$67.70
Purchase #2	$140.26	7.308%	$150.5102	$150.51	$150.50	$150.50
Purchase #3	$118.86	13.437%	$134.8312	$134.83	$134.85	$134.80
Purchase #4	$132.37	7.404%	$142.1707	$142.17	$142.15	$142.20
Purchase #5	$59.57	12.178%	$66.8244	$66.82	$66.80	$66.80
Purchase #6	$41.69	3.158%	$43.0066	$43.01	$43.00	$43.00
Purchase #7	$91.73	8.469%	$99.4986	$99.50	$99.50	$99.50
7 purchase totals =	$646.85		$704.5381	$704.54	$704.50	$704.50