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	$41.31	8.372%	$44.7685	$44.77	$44.75	$44.80
Purchase #2	$116.49	10.469%	$128.6853	$128.69	$128.70	$128.70
Purchase #3	$158.61	4.195%	$165.2637	$165.26	$165.25	$165.30
Purchase #4	$128.57	6.182%	$136.5182	$136.52	$136.50	$136.50
Purchase #5	$77.77	5.595%	$82.1212	$82.12	$82.10	$82.10
Purchase #6	$227.78	13.403%	$258.3094	$258.31	$258.30	$258.30
Purchase #7	$6.29	4.263%	$6.5581	$6.56	$6.55	$6.60
7 purchase totals =	$756.82		$822.2244	$822.23	$822.15	$822.30