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	$132.30	7.567%	$142.3111	$142.31	$142.30	$142.30
Purchase #2	$161.86	12.771%	$182.5311	$182.53	$182.55	$182.50
Purchase #3	$89.96	3.853%	$93.4262	$93.43	$93.45	$93.40
Purchase #4	$122.67	12.428%	$137.9154	$137.92	$137.90	$137.90
Purchase #5	$247.45	3.379%	$255.8113	$255.81	$255.80	$255.80
Purchase #6	$173.50	9.637%	$190.2202	$190.22	$190.20	$190.20
Purchase #7	$58.53	13.682%	$66.5381	$66.54	$66.55	$66.50
7 purchase totals =	$986.27		$1,068.7534	$1,068.76	$1,068.75	$1,068.60