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	$208.51	4.834%	$218.5894	$218.59	$218.60	$218.60
Purchase #2	$8.78	13.692%	$9.9822	$9.98	$10.00	$10.00
Purchase #3	$208.82	7.821%	$225.1518	$225.15	$225.15	$225.20
Purchase #4	$40.40	8.147%	$43.6914	$43.69	$43.70	$43.70
Purchase #5	$77.86	10.364%	$85.9294	$85.93	$85.95	$85.90
Purchase #6	$137.47	13.853%	$156.5137	$156.51	$156.50	$156.50
Purchase #7	$77.57	7.648%	$83.5026	$83.50	$83.50	$83.50
7 purchase totals =	$759.41		$823.3605	$823.35	$823.40	$823.40