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	$89.28	7.628%	$96.0903	$96.09	$96.10	$96.10
Purchase #2	$113.82	10.264%	$125.5025	$125.50	$125.50	$125.50
Purchase #3	$144.48	12.298%	$162.2482	$162.25	$162.25	$162.20
Purchase #4	$167.60	3.745%	$173.8766	$173.88	$173.90	$173.90
Purchase #5	$103.50	9.597%	$113.4329	$113.43	$113.45	$113.40
Purchase #6	$17.65	6.234%	$18.7503	$18.75	$18.75	$18.80
Purchase #7	$233.86	4.166%	$243.6026	$243.60	$243.60	$243.60
7 purchase totals =	$870.19		$933.5034	$933.50	$933.55	$933.50