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	$46.53	3.678%	$48.2414	$48.24	$48.25	$48.20
Purchase #2	$111.65	3.644%	$115.7185	$115.72	$115.70	$115.70
Purchase #3	$195.42	13.642%	$222.0792	$222.08	$222.10	$222.10
Purchase #4	$156.94	9.314%	$171.5574	$171.56	$171.55	$171.60
Purchase #5	$235.87	9.665%	$258.6668	$258.67	$258.65	$258.70
Purchase #6	$144.67	5.654%	$152.8496	$152.85	$152.85	$152.80
Purchase #7	$56.92	4.315%	$59.3761	$59.38	$59.40	$59.40
7 purchase totals =	$948.00		$1,028.4890	$1,028.50	$1,028.50	$1,028.50