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	$119.42	9.715%	$131.0217	$131.02	$131.00	$131.00
Purchase #2	$157.78	9.196%	$172.2894	$172.29	$172.30	$172.30
Purchase #3	$32.47	9.411%	$35.5258	$35.53	$35.55	$35.50
Purchase #4	$111.56	13.164%	$126.2458	$126.25	$126.25	$126.20
Purchase #5	$195.59	6.679%	$208.6535	$208.65	$208.65	$208.70
Purchase #6	$52.40	4.852%	$54.9424	$54.94	$54.95	$54.90
Purchase #7	$83.86	13.283%	$94.9991	$95.00	$95.00	$95.00
7 purchase totals =	$753.08		$823.6777	$823.68	$823.70	$823.60