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	$203.60	7.730%	$219.3383	$219.34	$219.35	$219.30
Purchase #2	$97.48	8.491%	$105.757	$105.76	$105.75	$105.80
Purchase #3	$218.47	3.607%	$226.3502	$226.35	$226.35	$226.40
Purchase #4	$47.66	6.671%	$50.8394	$50.84	$50.85	$50.80
Purchase #5	$17.34	5.347%	$18.2672	$18.27	$18.25	$18.30
Purchase #6	$78.72	13.743%	$89.5385	$89.54	$89.55	$89.50
Purchase #7	$175.74	9.662%	$192.72	$192.72	$192.70	$192.70
7 purchase totals =	$839.01		$902.8106	$902.82	$902.80	$902.80