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	$239.79	7.281%	$257.2491	$257.25	$257.25	$257.20
Purchase #2	$24.29	6.658%	$25.9072	$25.91	$25.90	$25.90
Purchase #3	$106.72	9.184%	$116.5212	$116.52	$116.50	$116.50
Purchase #4	$234.77	7.452%	$252.2651	$252.27	$252.25	$252.30
Purchase #5	$35.31	5.226%	$37.1553	$37.16	$37.15	$37.20
Purchase #6	$100.60	10.858%	$111.5231	$111.52	$111.50	$111.50
Purchase #7	$112.86	10.835%	$125.0884	$125.09	$125.10	$125.10
7 purchase totals =	$854.34		$925.7094	$925.72	$925.65	$925.70