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	$18.39	3.378%	$19.0112	$19.01	$19.00	$19.00
Purchase #2	$158.43	4.735%	$165.9317	$165.93	$165.95	$165.90
Purchase #3	$162.38	11.636%	$181.2745	$181.27	$181.25	$181.30
Purchase #4	$82.88	3.208%	$85.5388	$85.54	$85.55	$85.50
Purchase #5	$212.78	8.529%	$230.928	$230.93	$230.95	$230.90
Purchase #6	$9.72	12.674%	$10.9519	$10.95	$10.95	$11.00
Purchase #7	$56.60	10.257%	$62.4055	$62.41	$62.40	$62.40
7 purchase totals =	$701.18		$756.0416	$756.04	$756.05	$756.00