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	$100.47	5.434%	$105.9295	$105.93	$105.95	$105.90
Purchase #2	$207.51	11.585%	$231.55	$231.55	$231.55	$231.60
Purchase #3	$147.34	13.652%	$167.4549	$167.45	$167.45	$167.50
Purchase #4	$140.35	7.652%	$151.0896	$151.09	$151.10	$151.10
Purchase #5	$170.90	8.791%	$185.9238	$185.92	$185.90	$185.90
Purchase #6	$125.69	6.244%	$133.5381	$133.54	$133.55	$133.50
Purchase #7	$233.26	10.473%	$257.6893	$257.69	$257.70	$257.70
7 purchase totals =	$1,125.52		$1,233.1752	$1,233.17	$1,233.20	$1,233.20