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	$158.58	6.558%	$168.9797	$168.98	$169.00	$169.00
Purchase #2	$78.52	6.398%	$83.5437	$83.54	$83.55	$83.50
Purchase #3	$98.62	13.291%	$111.7276	$111.73	$111.75	$111.70
Purchase #4	$84.97	9.707%	$93.218	$93.22	$93.20	$93.20
Purchase #5	$105.50	13.498%	$119.7404	$119.74	$119.75	$119.70
Purchase #6	$119.30	4.454%	$124.6136	$124.61	$124.60	$124.60
Purchase #7	$50.32	4.870%	$52.7706	$52.77	$52.75	$52.80
7 purchase totals =	$695.81		$754.5936	$754.59	$754.60	$754.50