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	$86.88	10.280%	$95.8113	$95.81	$95.80	$95.80
Purchase #2	$217.84	5.695%	$230.246	$230.25	$230.25	$230.20
Purchase #3	$190.70	4.286%	$198.8734	$198.87	$198.85	$198.90
Purchase #4	$173.46	9.183%	$189.3888	$189.39	$189.40	$189.40
Purchase #5	$170.89	10.822%	$189.3837	$189.38	$189.40	$189.40
Purchase #6	$62.84	7.739%	$67.7032	$67.70	$67.70	$67.70
Purchase #7	$110.71	3.742%	$114.8528	$114.85	$114.85	$114.90
7 purchase totals =	$1,013.32		$1,086.2592	$1,086.25	$1,086.25	$1,086.30