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	$41.65	9.589%	$45.6438	$45.64	$45.65	$45.60
Purchase #2	$146.37	8.471%	$158.769	$158.77	$158.75	$158.80
Purchase #3	$124.27	10.753%	$137.6328	$137.63	$137.65	$137.60
Purchase #4	$159.52	5.661%	$168.5504	$168.55	$168.55	$168.60
Purchase #5	$30.54	3.524%	$31.6162	$31.62	$31.60	$31.60
Purchase #6	$64.65	6.286%	$68.7139	$68.71	$68.70	$68.70
Purchase #7	$227.39	7.111%	$243.5597	$243.56	$243.55	$243.60
7 purchase totals =	$794.39		$854.4858	$854.48	$854.45	$854.50