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	$112.88	11.173%	$125.4921	$125.49	$125.50	$125.50
Purchase #2	$227.35	12.263%	$255.2299	$255.23	$255.25	$255.20
Purchase #3	$78.84	4.652%	$82.5076	$82.51	$82.50	$82.50
Purchase #4	$37.68	7.636%	$40.5572	$40.56	$40.55	$40.60
Purchase #5	$134.57	6.691%	$143.5741	$143.57	$143.55	$143.60
Purchase #6	$194.60	7.688%	$209.5608	$209.56	$209.55	$209.60
Purchase #7	$44.85	7.625%	$48.2698	$48.27	$48.25	$48.30
7 purchase totals =	$830.77		$905.1915	$905.19	$905.15	$905.30