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	$22.86	9.464%	$25.0235	$25.02	$25.00	$25.00
Purchase #2	$57.90	3.228%	$59.769	$59.77	$59.75	$59.80
Purchase #3	$176.66	5.325%	$186.0671	$186.07	$186.05	$186.10
Purchase #4	$107.37	5.722%	$113.5137	$113.51	$113.50	$113.50
Purchase #5	$28.61	13.618%	$32.5061	$32.51	$32.50	$32.50
Purchase #6	$225.28	7.462%	$242.0904	$242.09	$242.10	$242.10
Purchase #7	$96.25	4.761%	$100.8325	$100.83	$100.85	$100.80
7 purchase totals =	$714.93		$759.8023	$759.80	$759.75	$759.80