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	$142.44	6.334%	$151.4621	$151.46	$151.45	$151.50
Purchase #2	$102.49	12.838%	$115.6477	$115.65	$115.65	$115.60
Purchase #3	$10.47	4.444%	$10.9353	$10.94	$10.95	$10.90
Purchase #4	$56.80	5.435%	$59.8871	$59.89	$59.90	$59.90
Purchase #5	$201.46	6.788%	$215.1351	$215.14	$215.15	$215.10
Purchase #6	$156.82	9.659%	$171.9672	$171.97	$171.95	$172.00
Purchase #7	$239.86	8.389%	$259.9819	$259.98	$260.00	$260.00
7 purchase totals =	$910.34		$985.0164	$985.03	$985.05	$985.00