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	$201.64	10.311%	$222.4311	$222.43	$222.45	$222.40
Purchase #2	$15.80	6.576%	$16.839	$16.84	$16.85	$16.80
Purchase #3	$33.58	11.390%	$37.4048	$37.40	$37.40	$37.40
Purchase #4	$50.70	8.196%	$54.8554	$54.86	$54.85	$54.90
Purchase #5	$31.42	5.579%	$33.1729	$33.17	$33.15	$33.20
Purchase #6	$194.87	4.520%	$203.6781	$203.68	$203.70	$203.70
Purchase #7	$180.83	8.527%	$196.2494	$196.25	$196.25	$196.20
7 purchase totals =	$708.84		$764.6307	$764.63	$764.65	$764.60