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	$231.44	5.229%	$243.542	$243.54	$243.55	$243.50
Purchase #2	$78.92	4.292%	$82.3072	$82.31	$82.30	$82.30
Purchase #3	$43.47	5.514%	$45.8669	$45.87	$45.85	$45.90
Purchase #4	$118.88	11.532%	$132.5892	$132.59	$132.60	$132.60
Purchase #5	$36.75	13.385%	$41.669	$41.67	$41.65	$41.70
Purchase #6	$194.44	9.768%	$213.4329	$213.43	$213.45	$213.40
Purchase #7	$137.76	11.810%	$154.0295	$154.03	$154.05	$154.00
7 purchase totals =	$841.66		$913.4367	$913.44	$913.45	$913.40