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	$67.81	7.265%	$72.7364	$72.74	$72.75	$72.70
Purchase #2	$111.79	11.522%	$124.6704	$124.67	$124.65	$124.70
Purchase #3	$128.93	9.709%	$141.4478	$141.45	$141.45	$141.40
Purchase #4	$133.71	13.725%	$152.0617	$152.06	$152.05	$152.10
Purchase #5	$175.92	5.432%	$185.476	$185.48	$185.50	$185.50
Purchase #6	$207.75	3.463%	$214.9444	$214.94	$214.95	$214.90
Purchase #7	$246.81	6.423%	$262.6626	$262.66	$262.65	$262.70
7 purchase totals =	$1,072.72		$1,153.9993	$1,154.00	$1,154.00	$1,154.00