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	$119.83	10.541%	$132.4613	$132.46	$132.45	$132.50
Purchase #2	$203.58	13.833%	$231.7412	$231.74	$231.75	$231.70
Purchase #3	$247.32	8.605%	$268.6019	$268.60	$268.60	$268.60
Purchase #4	$98.40	5.616%	$103.9261	$103.93	$103.95	$103.90
Purchase #5	$56.87	7.836%	$61.3263	$61.33	$61.35	$61.30
Purchase #6	$131.38	3.635%	$136.1557	$136.16	$136.15	$136.20
Purchase #7	$89.70	12.453%	$100.8703	$100.87	$100.85	$100.90
7 purchase totals =	$947.08		$1,035.0828	$1,035.09	$1,035.10	$1,035.10