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	$131.41	9.389%	$143.7481	$143.75	$143.75	$143.70
Purchase #2	$195.96	13.531%	$222.4753	$222.48	$222.50	$222.50
Purchase #3	$200.32	3.353%	$207.0367	$207.04	$207.05	$207.00
Purchase #4	$247.87	12.620%	$279.1512	$279.15	$279.15	$279.20
Purchase #5	$20.31	8.627%	$22.0621	$22.06	$22.05	$22.10
Purchase #6	$45.75	10.398%	$50.5071	$50.51	$50.50	$50.50
Purchase #7	$245.27	10.493%	$271.0062	$271.01	$271.00	$271.00
7 purchase totals =	$1,086.89		$1,195.9867	$1,196.00	$1,196.00	$1,196.00