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	$177.66	4.397%	$185.4717	$185.47	$185.45	$185.50
Purchase #2	$123.33	13.272%	$139.6984	$139.70	$139.70	$139.70
Purchase #3	$156.47	6.386%	$166.4622	$166.46	$166.45	$166.50
Purchase #4	$209.59	10.156%	$230.876	$230.88	$230.90	$230.90
Purchase #5	$79.66	11.725%	$89.0001	$89.00	$89.00	$89.00
Purchase #6	$127.41	10.214%	$140.4237	$140.42	$140.40	$140.40
Purchase #7	$201.70	13.414%	$228.756	$228.76	$228.75	$228.80
7 purchase totals =	$1,075.82		$1,180.6881	$1,180.69	$1,180.65	$1,180.80