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	$224.69	10.841%	$249.0486	$249.05	$249.05	$249.00
Purchase #2	$41.72	11.663%	$46.5858	$46.59	$46.60	$46.60
Purchase #3	$244.97	4.247%	$255.3739	$255.37	$255.35	$255.40
Purchase #4	$116.66	13.592%	$132.5164	$132.52	$132.50	$132.50
Purchase #5	$147.27	10.214%	$162.3122	$162.31	$162.30	$162.30
Purchase #6	$123.29	3.830%	$128.012	$128.01	$128.00	$128.00
Purchase #7	$185.49	6.151%	$196.8995	$196.90	$196.90	$196.90
7 purchase totals =	$1,084.09		$1,170.7484	$1,170.75	$1,170.70	$1,170.70