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	$13.78	3.611%	$14.2776	$14.28	$14.30	$14.30
Purchase #2	$65.90	13.627%	$74.8802	$74.88	$74.90	$74.90
Purchase #3	$208.93	10.348%	$230.5501	$230.55	$230.55	$230.60
Purchase #4	$183.48	4.120%	$191.0394	$191.04	$191.05	$191.00
Purchase #5	$64.93	10.563%	$71.7886	$71.79	$71.80	$71.80
Purchase #6	$173.68	13.175%	$196.5623	$196.56	$196.55	$196.60
Purchase #7	$101.33	9.649%	$111.1073	$111.11	$111.10	$111.10
7 purchase totals =	$812.03		$890.2055	$890.21	$890.25	$890.30