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	$120.40	11.497%	$134.2424	$134.24	$134.25	$134.20
Purchase #2	$60.77	11.685%	$67.871	$67.87	$67.85	$67.90
Purchase #3	$90.64	9.445%	$99.2009	$99.20	$99.20	$99.20
Purchase #4	$206.45	9.855%	$226.7956	$226.80	$226.80	$226.80
Purchase #5	$43.72	4.781%	$45.8103	$45.81	$45.80	$45.80
Purchase #6	$226.59	5.247%	$238.4792	$238.48	$238.50	$238.50
Purchase #7	$128.61	13.252%	$145.6534	$145.65	$145.65	$145.70
7 purchase totals =	$877.18		$958.0528	$958.05	$958.05	$958.10