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	$120.86	4.644%	$126.4727	$126.47	$126.45	$126.50
Purchase #2	$132.93	13.800%	$151.2743	$151.27	$151.25	$151.30
Purchase #3	$116.53	12.641%	$131.2606	$131.26	$131.25	$131.30
Purchase #4	$144.84	4.475%	$151.3216	$151.32	$151.30	$151.30
Purchase #5	$133.41	3.605%	$138.2194	$138.22	$138.20	$138.20
Purchase #6	$196.84	6.584%	$209.7999	$209.80	$209.80	$209.80
Purchase #7	$209.98	4.571%	$219.5782	$219.58	$219.60	$219.60
7 purchase totals =	$1,055.39		$1,127.9267	$1,127.92	$1,127.85	$1,128.00