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	$30.96	13.124%	$35.0232	$35.02	$35.00	$35.00
Purchase #2	$170.58	9.730%	$187.1774	$187.18	$187.20	$187.20
Purchase #3	$47.94	7.322%	$51.4502	$51.45	$51.45	$51.50
Purchase #4	$221.42	5.628%	$233.8815	$233.88	$233.90	$233.90
Purchase #5	$80.49	12.810%	$90.8008	$90.80	$90.80	$90.80
Purchase #6	$129.28	6.336%	$137.4712	$137.47	$137.45	$137.50
Purchase #7	$115.77	13.652%	$131.5749	$131.57	$131.55	$131.60
7 purchase totals =	$796.44		$867.3792	$867.37	$867.35	$867.50