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	$93.57	5.503%	$98.7192	$98.72	$98.70	$98.70
Purchase #2	$14.78	11.431%	$16.4695	$16.47	$16.45	$16.50
Purchase #3	$103.66	8.835%	$112.8184	$112.82	$112.80	$112.80
Purchase #4	$33.72	4.173%	$35.1271	$35.13	$35.15	$35.10
Purchase #5	$55.43	7.264%	$59.4564	$59.46	$59.45	$59.50
Purchase #6	$190.87	8.624%	$207.3306	$207.33	$207.35	$207.30
Purchase #7	$145.90	8.666%	$158.5437	$158.54	$158.55	$158.50
7 purchase totals =	$637.93		$688.4649	$688.47	$688.45	$688.40