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	$205.35	8.559%	$222.9259	$222.93	$222.95	$222.90
Purchase #2	$108.28	12.318%	$121.6179	$121.62	$121.60	$121.60
Purchase #3	$98.83	6.833%	$105.5831	$105.58	$105.60	$105.60
Purchase #4	$213.66	13.181%	$241.8225	$241.82	$241.80	$241.80
Purchase #5	$79.96	11.425%	$89.0954	$89.10	$89.10	$89.10
Purchase #6	$163.94	11.836%	$183.3439	$183.34	$183.35	$183.30
Purchase #7	$196.70	9.546%	$215.477	$215.48	$215.50	$215.50
7 purchase totals =	$1,066.72		$1,179.8657	$1,179.87	$1,179.90	$1,179.80