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	$195.61	13.735%	$222.477	$222.48	$222.50	$222.50
Purchase #2	$138.25	11.507%	$154.1584	$154.16	$154.15	$154.20
Purchase #3	$194.85	7.377%	$209.2241	$209.22	$209.20	$209.20
Purchase #4	$138.32	4.112%	$144.0077	$144.01	$144.00	$144.00
Purchase #5	$155.27	11.265%	$172.7612	$172.76	$172.75	$172.80
Purchase #6	$226.81	9.368%	$248.0576	$248.06	$248.05	$248.10
Purchase #7	$116.26	12.853%	$131.2029	$131.20	$131.20	$131.20
7 purchase totals =	$1,165.37		$1,281.8889	$1,281.89	$1,281.85	$1,282.00