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	$55.47	5.565%	$58.5569	$58.56	$58.55	$58.60
Purchase #2	$45.50	6.298%	$48.3656	$48.37	$48.35	$48.40
Purchase #3	$12.78	13.250%	$14.4734	$14.47	$14.45	$14.50
Purchase #4	$94.85	3.159%	$97.8463	$97.85	$97.85	$97.80
Purchase #5	$87.67	9.262%	$95.79	$95.79	$95.80	$95.80
Purchase #6	$87.38	8.181%	$94.5286	$94.53	$94.55	$94.50
Purchase #7	$38.30	10.481%	$42.3142	$42.31	$42.30	$42.30
7 purchase totals =	$421.95		$451.8750	$451.88	$451.85	$451.90