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	$218.33	3.689%	$226.3842	$226.38	$226.40	$226.40
Purchase #2	$67.91	5.317%	$71.5208	$71.52	$71.50	$71.50
Purchase #3	$37.32	10.536%	$41.252	$41.25	$41.25	$41.30
Purchase #4	$25.59	11.286%	$28.4781	$28.48	$28.50	$28.50
Purchase #5	$132.94	4.160%	$138.4703	$138.47	$138.45	$138.50
Purchase #6	$199.45	11.469%	$222.3249	$222.32	$222.30	$222.30
Purchase #7	$225.33	13.409%	$255.5445	$255.54	$255.55	$255.50
7 purchase totals =	$906.87		$983.9748	$983.96	$983.95	$984.00