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	$230.50	12.392%	$259.0636	$259.06	$259.05	$259.10
Purchase #2	$79.88	12.267%	$89.6789	$89.68	$89.70	$89.70
Purchase #3	$103.42	8.259%	$111.9615	$111.96	$111.95	$112.00
Purchase #4	$164.90	4.254%	$171.9148	$171.91	$171.90	$171.90
Purchase #5	$187.91	3.384%	$194.2689	$194.27	$194.25	$194.30
Purchase #6	$131.58	6.613%	$140.2814	$140.28	$140.30	$140.30
Purchase #7	$134.48	4.556%	$140.6069	$140.61	$140.60	$140.60
7 purchase totals =	$1,032.67		$1,107.7760	$1,107.77	$1,107.75	$1,107.90