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	$94.77	11.385%	$105.5596	$105.56	$105.55	$105.60
Purchase #2	$104.61	13.382%	$118.6089	$118.61	$118.60	$118.60
Purchase #3	$36.52	11.162%	$40.5964	$40.60	$40.60	$40.60
Purchase #4	$20.77	3.457%	$21.488	$21.49	$21.50	$21.50
Purchase #5	$47.33	8.747%	$51.47	$51.47	$51.45	$51.50
Purchase #6	$132.60	7.394%	$142.4044	$142.40	$142.40	$142.40
Purchase #7	$183.59	8.424%	$199.0556	$199.06	$199.05	$199.10
7 purchase totals =	$620.19		$679.1829	$679.19	$679.15	$679.30