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	$81.39	6.711%	$86.8521	$86.85	$86.85	$86.90
Purchase #2	$53.78	11.268%	$59.8399	$59.84	$59.85	$59.80
Purchase #3	$177.66	10.461%	$196.245	$196.25	$196.25	$196.20
Purchase #4	$96.49	8.706%	$104.8904	$104.89	$104.90	$104.90
Purchase #5	$129.92	7.183%	$139.2522	$139.25	$139.25	$139.30
Purchase #6	$203.87	8.691%	$221.5883	$221.59	$221.60	$221.60
Purchase #7	$182.48	9.490%	$199.7974	$199.80	$199.80	$199.80
7 purchase totals =	$925.59		$1,008.4653	$1,008.47	$1,008.50	$1,008.50