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	$138.63	8.504%	$150.4191	$150.42	$150.40	$150.40
Purchase #2	$18.81	4.265%	$19.6122	$19.61	$19.60	$19.60
Purchase #3	$56.32	9.318%	$61.5679	$61.57	$61.55	$61.60
Purchase #4	$114.39	4.605%	$119.6577	$119.66	$119.65	$119.70
Purchase #5	$237.75	13.406%	$269.6228	$269.62	$269.60	$269.60
Purchase #6	$204.71	11.369%	$227.9835	$227.98	$228.00	$228.00
Purchase #7	$165.72	11.389%	$184.5939	$184.59	$184.60	$184.60
7 purchase totals =	$936.33		$1,033.4571	$1,033.45	$1,033.40	$1,033.50