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	$23.73	8.783%	$25.8142	$25.81	$25.80	$25.80
Purchase #2	$66.49	12.239%	$74.6277	$74.63	$74.65	$74.60
Purchase #3	$100.90	10.280%	$111.2725	$111.27	$111.25	$111.30
Purchase #4	$64.74	11.425%	$72.1365	$72.14	$72.15	$72.10
Purchase #5	$175.66	12.105%	$196.9236	$196.92	$196.90	$196.90
Purchase #6	$219.94	3.873%	$228.4583	$228.46	$228.45	$228.50
Purchase #7	$22.93	13.852%	$26.1063	$26.11	$26.10	$26.10
7 purchase totals =	$674.39		$735.3391	$735.34	$735.30	$735.30