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	$220.43	8.654%	$239.506	$239.51	$239.50	$239.50
Purchase #2	$26.43	3.868%	$27.4523	$27.45	$27.45	$27.50
Purchase #3	$106.90	5.388%	$112.6598	$112.66	$112.65	$112.70
Purchase #4	$52.69	12.406%	$59.2267	$59.23	$59.25	$59.20
Purchase #5	$57.40	8.772%	$62.4351	$62.44	$62.45	$62.40
Purchase #6	$218.94	3.164%	$225.8673	$225.87	$225.85	$225.90
Purchase #7	$221.42	9.393%	$242.218	$242.22	$242.20	$242.20
7 purchase totals =	$904.21		$969.3652	$969.38	$969.35	$969.40