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	$48.40	7.547%	$52.0527	$52.05	$52.05	$52.10
Purchase #2	$226.78	8.862%	$246.8772	$246.88	$246.90	$246.90
Purchase #3	$26.79	6.372%	$28.4971	$28.50	$28.50	$28.50
Purchase #4	$15.88	10.164%	$17.494	$17.49	$17.50	$17.50
Purchase #5	$85.84	4.609%	$89.7964	$89.80	$89.80	$89.80
Purchase #6	$158.29	8.853%	$172.3034	$172.30	$172.30	$172.30
Purchase #7	$28.65	13.259%	$32.4487	$32.45	$32.45	$32.40
7 purchase totals =	$590.63		$639.4695	$639.47	$639.50	$639.50