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	$160.66	10.583%	$177.6626	$177.66	$177.65	$177.70
Purchase #2	$94.54	12.856%	$106.6941	$106.69	$106.70	$106.70
Purchase #3	$89.88	5.209%	$94.5618	$94.56	$94.55	$94.60
Purchase #4	$202.52	9.839%	$222.4459	$222.45	$222.45	$222.40
Purchase #5	$18.59	12.196%	$20.8572	$20.86	$20.85	$20.90
Purchase #6	$104.82	13.706%	$119.1866	$119.19	$119.20	$119.20
Purchase #7	$189.73	5.105%	$199.4157	$199.42	$199.40	$199.40
7 purchase totals =	$860.74		$940.8239	$940.83	$940.80	$940.90