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	$207.77	11.365%	$231.3831	$231.38	$231.40	$231.40
Purchase #2	$136.72	6.448%	$145.5357	$145.54	$145.55	$145.50
Purchase #3	$82.70	9.366%	$90.4457	$90.45	$90.45	$90.40
Purchase #4	$54.94	3.263%	$56.7327	$56.73	$56.75	$56.70
Purchase #5	$225.66	3.453%	$233.452	$233.45	$233.45	$233.50
Purchase #6	$151.30	8.842%	$164.6779	$164.68	$164.70	$164.70
Purchase #7	$99.95	6.570%	$106.5167	$106.52	$106.50	$106.50
7 purchase totals =	$959.04		$1,028.7438	$1,028.75	$1,028.80	$1,028.70