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	$167.52	8.547%	$181.8379	$181.84	$181.85	$181.80
Purchase #2	$134.81	3.575%	$139.6295	$139.63	$139.65	$139.60
Purchase #3	$74.93	4.346%	$78.1865	$78.19	$78.20	$78.20
Purchase #4	$99.31	9.235%	$108.4813	$108.48	$108.50	$108.50
Purchase #5	$97.25	9.153%	$106.1513	$106.15	$106.15	$106.20
Purchase #6	$186.49	4.521%	$194.9212	$194.92	$194.90	$194.90
Purchase #7	$136.50	11.809%	$152.6193	$152.62	$152.60	$152.60
7 purchase totals =	$896.81		$961.8270	$961.83	$961.85	$961.80