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	$65.80	10.259%	$72.5504	$72.55	$72.55	$72.60
Purchase #2	$250.67	10.544%	$277.1006	$277.10	$277.10	$277.10
Purchase #3	$135.43	13.139%	$153.2241	$153.22	$153.20	$153.20
Purchase #4	$135.50	5.527%	$142.9891	$142.99	$143.00	$143.00
Purchase #5	$79.59	11.272%	$88.5614	$88.56	$88.55	$88.60
Purchase #6	$208.98	5.201%	$219.849	$219.85	$219.85	$219.80
Purchase #7	$99.92	11.477%	$111.3878	$111.39	$111.40	$111.40
7 purchase totals =	$975.89		$1,065.6624	$1,065.66	$1,065.65	$1,065.70