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	$133.76	7.699%	$144.0582	$144.06	$144.05	$144.10
Purchase #2	$9.59	9.285%	$10.4804	$10.48	$10.50	$10.50
Purchase #3	$98.59	7.469%	$105.9537	$105.95	$105.95	$106.00
Purchase #4	$82.56	8.401%	$89.4959	$89.50	$89.50	$89.50
Purchase #5	$132.39	8.425%	$143.5439	$143.54	$143.55	$143.50
Purchase #6	$22.84	13.188%	$25.8521	$25.85	$25.85	$25.90
Purchase #7	$247.25	12.826%	$278.9623	$278.96	$278.95	$279.00
7 purchase totals =	$726.98		$798.3465	$798.34	$798.35	$798.50