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	$108.61	3.674%	$112.6003	$112.60	$112.60	$112.60
Purchase #2	$21.99	3.178%	$22.6888	$22.69	$22.70	$22.70
Purchase #3	$91.43	5.634%	$96.5812	$96.58	$96.60	$96.60
Purchase #4	$109.79	8.481%	$119.1013	$119.10	$119.10	$119.10
Purchase #5	$190.49	4.715%	$199.4716	$199.47	$199.45	$199.50
Purchase #6	$163.83	10.855%	$181.6137	$181.61	$181.60	$181.60
Purchase #7	$36.61	13.237%	$41.4561	$41.46	$41.45	$41.50
7 purchase totals =	$722.75		$773.5130	$773.51	$773.50	$773.60