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	$137.45	11.820%	$153.6966	$153.70	$153.70	$153.70
Purchase #2	$164.29	5.594%	$173.4804	$173.48	$173.50	$173.50
Purchase #3	$237.92	10.288%	$262.3972	$262.40	$262.40	$262.40
Purchase #4	$203.69	5.769%	$215.4409	$215.44	$215.45	$215.40
Purchase #5	$164.91	13.645%	$187.412	$187.41	$187.40	$187.40
Purchase #6	$136.65	5.688%	$144.4227	$144.42	$144.40	$144.40
Purchase #7	$41.25	13.628%	$46.8716	$46.87	$46.85	$46.90
7 purchase totals =	$1,086.16		$1,183.7214	$1,183.72	$1,183.70	$1,183.70