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	$224.63	13.524%	$255.009	$255.01	$255.00	$255.00
Purchase #2	$215.47	11.781%	$240.8545	$240.85	$240.85	$240.90
Purchase #3	$111.52	13.103%	$126.1325	$126.13	$126.15	$126.10
Purchase #4	$196.68	4.268%	$205.0743	$205.07	$205.05	$205.10
Purchase #5	$143.48	11.695%	$160.26	$160.26	$160.25	$160.30
Purchase #6	$194.85	3.102%	$200.8942	$200.89	$200.90	$200.90
Purchase #7	$162.43	13.719%	$184.7138	$184.71	$184.70	$184.70
7 purchase totals =	$1,249.06		$1,372.9383	$1,372.92	$1,372.90	$1,373.00