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	$114.57	8.115%	$123.8674	$123.87	$123.85	$123.90
Purchase #2	$231.88	7.264%	$248.7238	$248.72	$248.70	$248.70
Purchase #3	$78.92	8.613%	$85.7174	$85.72	$85.70	$85.70
Purchase #4	$36.82	10.177%	$40.5672	$40.57	$40.55	$40.60
Purchase #5	$147.64	8.260%	$159.8351	$159.84	$159.85	$159.80
Purchase #6	$81.80	13.115%	$92.5281	$92.53	$92.55	$92.50
Purchase #7	$182.40	12.611%	$205.4025	$205.40	$205.40	$205.40
7 purchase totals =	$874.03		$956.6415	$956.65	$956.60	$956.60