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	$9.60	7.123%	$10.2838	$10.28	$10.30	$10.30
Purchase #2	$28.94	12.674%	$32.6079	$32.61	$32.60	$32.60
Purchase #3	$113.73	4.618%	$118.9821	$118.98	$119.00	$119.00
Purchase #4	$235.78	4.633%	$246.7037	$246.70	$246.70	$246.70
Purchase #5	$132.75	3.276%	$137.0989	$137.10	$137.10	$137.10
Purchase #6	$119.93	9.276%	$131.0547	$131.05	$131.05	$131.10
Purchase #7	$181.42	5.609%	$191.5958	$191.60	$191.60	$191.60
7 purchase totals =	$822.15		$868.3269	$868.32	$868.35	$868.40