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	$90.67	7.244%	$97.2381	$97.24	$97.25	$97.20
Purchase #2	$80.33	6.141%	$85.2631	$85.26	$85.25	$85.30
Purchase #3	$223.34	8.149%	$241.54	$241.54	$241.55	$241.50
Purchase #4	$38.75	4.739%	$40.5864	$40.59	$40.60	$40.60
Purchase #5	$17.30	8.545%	$18.7783	$18.78	$18.80	$18.80
Purchase #6	$22.97	12.301%	$25.7955	$25.80	$25.80	$25.80
Purchase #7	$46.47	6.738%	$49.6011	$49.60	$49.60	$49.60
7 purchase totals =	$519.83		$558.8025	$558.81	$558.85	$558.80