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	$50.26	8.123%	$54.3426	$54.34	$54.35	$54.30
Purchase #2	$13.80	8.783%	$15.0121	$15.01	$15.00	$15.00
Purchase #3	$83.96	6.654%	$89.5467	$89.55	$89.55	$89.50
Purchase #4	$224.54	4.727%	$235.154	$235.15	$235.15	$235.20
Purchase #5	$158.29	4.263%	$165.0379	$165.04	$165.05	$165.00
Purchase #6	$191.89	4.826%	$201.1506	$201.15	$201.15	$201.20
Purchase #7	$116.95	5.492%	$123.3729	$123.37	$123.35	$123.40
7 purchase totals =	$839.69		$883.6168	$883.61	$883.60	$883.60