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	$150.37	5.527%	$158.6809	$158.68	$158.70	$158.70
Purchase #2	$233.63	12.147%	$262.009	$262.01	$262.00	$262.00
Purchase #3	$145.89	10.177%	$160.7372	$160.74	$160.75	$160.70
Purchase #4	$62.88	7.492%	$67.591	$67.59	$67.60	$67.60
Purchase #5	$11.44	6.218%	$12.1513	$12.15	$12.15	$12.20
Purchase #6	$73.59	7.161%	$78.8598	$78.86	$78.85	$78.90
Purchase #7	$100.37	12.681%	$113.0979	$113.10	$113.10	$113.10
7 purchase totals =	$778.17		$853.1271	$853.13	$853.15	$853.20