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	$200.40	12.651%	$225.7526	$225.75	$225.75	$225.80
Purchase #2	$233.87	11.397%	$260.5242	$260.52	$260.50	$260.50
Purchase #3	$136.37	11.477%	$152.0212	$152.02	$152.00	$152.00
Purchase #4	$100.28	13.503%	$113.8208	$113.82	$113.80	$113.80
Purchase #5	$234.28	6.738%	$250.0658	$250.07	$250.05	$250.10
Purchase #6	$61.64	6.790%	$65.8254	$65.83	$65.85	$65.80
Purchase #7	$89.55	3.285%	$92.4917	$92.49	$92.50	$92.50
7 purchase totals =	$1,056.39		$1,160.5017	$1,160.50	$1,160.45	$1,160.50