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	$231.81	13.620%	$263.3825	$263.38	$263.40	$263.40
Purchase #2	$40.35	4.421%	$42.1339	$42.13	$42.15	$42.10
Purchase #3	$149.82	4.838%	$157.0683	$157.07	$157.05	$157.10
Purchase #4	$44.84	6.565%	$47.7837	$47.78	$47.80	$47.80
Purchase #5	$80.26	11.755%	$89.6946	$89.69	$89.70	$89.70
Purchase #6	$19.59	9.280%	$21.408	$21.41	$21.40	$21.40
Purchase #7	$63.47	11.220%	$70.5913	$70.59	$70.60	$70.60
7 purchase totals =	$630.14		$692.0623	$692.05	$692.10	$692.10