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	$190.86	13.785%	$217.1701	$217.17	$217.15	$217.20
Purchase #2	$128.39	11.616%	$143.3038	$143.30	$143.30	$143.30
Purchase #3	$195.76	5.181%	$205.9023	$205.90	$205.90	$205.90
Purchase #4	$122.83	4.493%	$128.3488	$128.35	$128.35	$128.30
Purchase #5	$95.31	3.366%	$98.5181	$98.52	$98.50	$98.50
Purchase #6	$42.96	4.848%	$45.0427	$45.04	$45.05	$45.00
Purchase #7	$250.95	7.364%	$269.43	$269.43	$269.45	$269.40
7 purchase totals =	$1,027.06		$1,107.7158	$1,107.71	$1,107.70	$1,107.60