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	$40.35	8.381%	$43.7317	$43.73	$43.75	$43.70
Purchase #2	$179.99	5.832%	$190.487	$190.49	$190.50	$190.50
Purchase #3	$212.25	5.269%	$223.4335	$223.43	$223.45	$223.40
Purchase #4	$152.31	9.205%	$166.3301	$166.33	$166.35	$166.30
Purchase #5	$84.90	11.203%	$94.4113	$94.41	$94.40	$94.40
Purchase #6	$170.50	6.256%	$181.1665	$181.17	$181.15	$181.20
Purchase #7	$127.89	6.805%	$136.5929	$136.59	$136.60	$136.60
7 purchase totals =	$968.19		$1,036.1530	$1,036.15	$1,036.20	$1,036.10