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	$83.90	13.611%	$95.3196	$95.32	$95.30	$95.30
Purchase #2	$27.25	3.816%	$28.2899	$28.29	$28.30	$28.30
Purchase #3	$196.51	4.615%	$205.5789	$205.58	$205.60	$205.60
Purchase #4	$12.37	12.556%	$13.9232	$13.92	$13.90	$13.90
Purchase #5	$79.89	12.395%	$89.7924	$89.79	$89.80	$89.80
Purchase #6	$39.41	8.268%	$42.6684	$42.67	$42.65	$42.70
Purchase #7	$169.48	13.839%	$192.9343	$192.93	$192.95	$192.90
7 purchase totals =	$608.81		$668.5067	$668.50	$668.50	$668.50