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	$207.67	7.416%	$223.0708	$223.07	$223.05	$223.10
Purchase #2	$214.31	3.707%	$222.2545	$222.25	$222.25	$222.30
Purchase #3	$72.38	8.463%	$78.5055	$78.51	$78.50	$78.50
Purchase #4	$201.54	3.729%	$209.0554	$209.06	$209.05	$209.10
Purchase #5	$16.56	9.257%	$18.093	$18.09	$18.10	$18.10
Purchase #6	$136.98	10.801%	$151.7752	$151.78	$151.80	$151.80
Purchase #7	$37.46	8.240%	$40.5467	$40.55	$40.55	$40.50
7 purchase totals =	$886.90		$943.3011	$943.31	$943.30	$943.40