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	$129.40	9.406%	$141.5714	$141.57	$141.55	$141.60
Purchase #2	$72.49	13.416%	$82.2153	$82.22	$82.20	$82.20
Purchase #3	$48.64	11.695%	$54.3284	$54.33	$54.35	$54.30
Purchase #4	$169.39	3.452%	$175.2373	$175.24	$175.25	$175.20
Purchase #5	$128.42	13.158%	$145.3175	$145.32	$145.30	$145.30
Purchase #6	$159.61	3.766%	$165.6209	$165.62	$165.60	$165.60
Purchase #7	$161.63	13.606%	$183.6214	$183.62	$183.60	$183.60
7 purchase totals =	$869.58		$947.9122	$947.92	$947.85	$947.80