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	$219.47	11.377%	$244.4391	$244.44	$244.45	$244.40
Purchase #2	$156.49	13.444%	$177.5285	$177.53	$177.55	$177.50
Purchase #3	$197.37	12.701%	$222.438	$222.44	$222.45	$222.40
Purchase #4	$100.59	5.305%	$105.9263	$105.93	$105.95	$105.90
Purchase #5	$149.75	4.589%	$156.622	$156.62	$156.60	$156.60
Purchase #6	$118.46	4.397%	$123.6687	$123.67	$123.65	$123.70
Purchase #7	$41.84	3.249%	$43.1994	$43.20	$43.20	$43.20
7 purchase totals =	$983.97		$1,073.8220	$1,073.83	$1,073.85	$1,073.70