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	$110.80	11.235%	$123.2484	$123.25	$123.25	$123.20
Purchase #2	$69.72	12.594%	$78.5005	$78.50	$78.50	$78.50
Purchase #3	$128.30	3.259%	$132.4813	$132.48	$132.50	$132.50
Purchase #4	$239.74	13.570%	$272.2727	$272.27	$272.25	$272.30
Purchase #5	$154.69	12.811%	$174.5073	$174.51	$174.50	$174.50
Purchase #6	$215.99	10.754%	$239.2176	$239.22	$239.20	$239.20
Purchase #7	$94.65	9.337%	$103.4875	$103.49	$103.50	$103.50
7 purchase totals =	$1,013.89		$1,123.7153	$1,123.72	$1,123.70	$1,123.70