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	$58.65	12.208%	$65.81	$65.81	$65.80	$65.80
Purchase #2	$224.37	5.725%	$237.2152	$237.22	$237.20	$237.20
Purchase #3	$10.78	6.107%	$11.4383	$11.44	$11.45	$11.40
Purchase #4	$115.90	10.720%	$128.3245	$128.32	$128.30	$128.30
Purchase #5	$222.28	3.247%	$229.4974	$229.50	$229.50	$229.50
Purchase #6	$198.45	3.413%	$205.2231	$205.22	$205.20	$205.20
Purchase #7	$188.50	4.151%	$196.3246	$196.32	$196.30	$196.30
7 purchase totals =	$1,018.93		$1,073.8331	$1,073.83	$1,073.75	$1,073.70