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	$148.59	3.275%	$153.4563	$153.46	$153.45	$153.50
Purchase #2	$209.89	6.458%	$223.4447	$223.44	$223.45	$223.40
Purchase #3	$151.25	13.443%	$171.5825	$171.58	$171.60	$171.60
Purchase #4	$7.90	6.874%	$8.443	$8.44	$8.45	$8.40
Purchase #5	$233.77	10.360%	$257.9886	$257.99	$258.00	$258.00
Purchase #6	$75.35	9.629%	$82.6055	$82.61	$82.60	$82.60
Purchase #7	$10.70	8.206%	$11.578	$11.58	$11.60	$11.60
7 purchase totals =	$837.45		$909.0986	$909.10	$909.15	$909.10