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	$158.46	9.433%	$173.4075	$173.41	$173.40	$173.40
Purchase #2	$130.92	10.345%	$144.4637	$144.46	$144.45	$144.50
Purchase #3	$102.60	10.654%	$113.531	$113.53	$113.55	$113.50
Purchase #4	$48.35	10.481%	$53.4176	$53.42	$53.40	$53.40
Purchase #5	$43.56	11.633%	$48.6273	$48.63	$48.65	$48.60
Purchase #6	$44.80	9.151%	$48.8996	$48.90	$48.90	$48.90
Purchase #7	$41.46	10.656%	$45.878	$45.88	$45.90	$45.90
7 purchase totals =	$570.15		$628.2247	$628.23	$628.25	$628.20