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	$57.28	4.499%	$59.857	$59.86	$59.85	$59.90
Purchase #2	$228.86	3.333%	$236.4879	$236.49	$236.50	$236.50
Purchase #3	$80.31	12.668%	$90.4837	$90.48	$90.50	$90.50
Purchase #4	$176.57	6.509%	$188.0629	$188.06	$188.05	$188.10
Purchase #5	$197.57	7.317%	$212.0262	$212.03	$212.05	$212.00
Purchase #6	$132.39	9.300%	$144.7023	$144.70	$144.70	$144.70
Purchase #7	$69.82	5.478%	$73.6447	$73.64	$73.65	$73.60
7 purchase totals =	$942.80		$1,005.2647	$1,005.26	$1,005.30	$1,005.30