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	$132.94	6.643%	$141.7712	$141.77	$141.75	$141.80
Purchase #2	$151.60	4.664%	$158.6706	$158.67	$158.65	$158.70
Purchase #3	$209.48	6.687%	$223.4879	$223.49	$223.50	$223.50
Purchase #4	$116.30	13.231%	$131.6877	$131.69	$131.70	$131.70
Purchase #5	$142.60	9.367%	$155.9573	$155.96	$155.95	$156.00
Purchase #6	$160.37	12.564%	$180.5189	$180.52	$180.50	$180.50
Purchase #7	$230.28	11.517%	$256.8013	$256.80	$256.80	$256.80
7 purchase totals =	$1,143.57		$1,248.8949	$1,248.90	$1,248.85	$1,249.00