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	$194.79	5.677%	$205.8482	$205.85	$205.85	$205.80
Purchase #2	$209.49	3.430%	$216.6755	$216.68	$216.70	$216.70
Purchase #3	$128.41	8.719%	$139.6061	$139.61	$139.60	$139.60
Purchase #4	$245.26	4.182%	$255.5168	$255.52	$255.50	$255.50
Purchase #5	$83.99	13.554%	$95.374	$95.37	$95.35	$95.40
Purchase #6	$131.54	7.564%	$141.4897	$141.49	$141.50	$141.50
Purchase #7	$79.55	8.568%	$86.3658	$86.37	$86.35	$86.40
7 purchase totals =	$1,073.03		$1,140.8761	$1,140.89	$1,140.85	$1,140.90