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	$221.71	9.194%	$242.094	$242.09	$242.10	$242.10
Purchase #2	$182.52	3.853%	$189.5525	$189.55	$189.55	$189.60
Purchase #3	$62.37	12.791%	$70.3477	$70.35	$70.35	$70.30
Purchase #4	$137.49	6.606%	$146.5726	$146.57	$146.55	$146.60
Purchase #5	$51.57	5.593%	$54.4543	$54.45	$54.45	$54.50
Purchase #6	$107.50	5.255%	$113.1491	$113.15	$113.15	$113.10
Purchase #7	$248.43	12.358%	$279.131	$279.13	$279.15	$279.10
7 purchase totals =	$1,011.59		$1,095.3012	$1,095.29	$1,095.30	$1,095.30