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	$162.60	7.214%	$174.33	$174.33	$174.35	$174.30
Purchase #2	$199.71	4.373%	$208.4433	$208.44	$208.45	$208.40
Purchase #3	$123.34	3.165%	$127.2437	$127.24	$127.25	$127.20
Purchase #4	$102.59	4.683%	$107.3943	$107.39	$107.40	$107.40
Purchase #5	$124.65	5.147%	$131.0657	$131.07	$131.05	$131.10
Purchase #6	$172.84	7.396%	$185.6232	$185.62	$185.60	$185.60
Purchase #7	$79.58	3.579%	$82.4282	$82.43	$82.45	$82.40
7 purchase totals =	$965.31		$1,016.5284	$1,016.52	$1,016.55	$1,016.40