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	$227.61	5.396%	$239.8918	$239.89	$239.90	$239.90
Purchase #2	$79.83	4.796%	$83.6586	$83.66	$83.65	$83.70
Purchase #3	$120.45	9.420%	$131.7964	$131.80	$131.80	$131.80
Purchase #4	$151.31	4.728%	$158.4639	$158.46	$158.45	$158.50
Purchase #5	$127.82	4.389%	$133.43	$133.43	$133.45	$133.40
Purchase #6	$224.43	9.323%	$245.3536	$245.35	$245.35	$245.40
Purchase #7	$116.58	13.481%	$132.2961	$132.30	$132.30	$132.30
7 purchase totals =	$1,048.03		$1,124.8904	$1,124.89	$1,124.90	$1,125.00