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	$107.55	3.691%	$111.5197	$111.52	$111.50	$111.50
Purchase #2	$160.60	3.551%	$166.3029	$166.30	$166.30	$166.30
Purchase #3	$236.55	8.504%	$256.6662	$256.67	$256.65	$256.70
Purchase #4	$118.32	13.208%	$133.9477	$133.95	$133.95	$133.90
Purchase #5	$243.78	9.358%	$266.5929	$266.59	$266.60	$266.60
Purchase #6	$147.99	5.767%	$156.5246	$156.52	$156.50	$156.50
Purchase #7	$112.59	5.242%	$118.492	$118.49	$118.50	$118.50
7 purchase totals =	$1,127.38		$1,210.0460	$1,210.04	$1,210.00	$1,210.00