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	$9.95	13.616%	$11.3048	$11.30	$11.30	$11.30
Purchase #2	$97.75	11.220%	$108.7176	$108.72	$108.70	$108.70
Purchase #3	$138.47	11.337%	$154.1683	$154.17	$154.15	$154.20
Purchase #4	$168.72	13.610%	$191.6828	$191.68	$191.70	$191.70
Purchase #5	$219.85	7.804%	$237.0071	$237.01	$237.00	$237.00
Purchase #6	$79.96	11.747%	$89.3529	$89.35	$89.35	$89.40
Purchase #7	$203.81	10.209%	$224.617	$224.62	$224.60	$224.60
7 purchase totals =	$918.51		$1,016.8505	$1,016.85	$1,016.80	$1,016.90