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	$208.58	11.622%	$232.8212	$232.82	$232.80	$232.80
Purchase #2	$56.69	8.437%	$61.4729	$61.47	$61.45	$61.50
Purchase #3	$104.66	4.727%	$109.6073	$109.61	$109.60	$109.60
Purchase #4	$243.87	9.662%	$267.4327	$267.43	$267.45	$267.40
Purchase #5	$60.29	7.779%	$64.98	$64.98	$65.00	$65.00
Purchase #6	$37.72	3.224%	$38.9361	$38.94	$38.95	$38.90
Purchase #7	$248.46	10.537%	$274.6402	$274.64	$274.65	$274.60
7 purchase totals =	$960.27		$1,049.8904	$1,049.89	$1,049.90	$1,049.80