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	$194.57	4.530%	$203.384	$203.38	$203.40	$203.40
Purchase #2	$81.86	9.775%	$89.8618	$89.86	$89.85	$89.90
Purchase #3	$216.45	10.780%	$239.7833	$239.78	$239.80	$239.80
Purchase #4	$76.89	11.226%	$85.5217	$85.52	$85.50	$85.50
Purchase #5	$92.38	12.296%	$103.739	$103.74	$103.75	$103.70
Purchase #6	$87.31	5.583%	$92.1845	$92.18	$92.20	$92.20
Purchase #7	$250.92	13.656%	$285.1856	$285.19	$285.20	$285.20
7 purchase totals =	$1,000.38		$1,099.6599	$1,099.65	$1,099.70	$1,099.70