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	$45.62	5.132%	$47.9612	$47.96	$47.95	$48.00
Purchase #2	$180.52	10.738%	$199.9042	$199.90	$199.90	$199.90
Purchase #3	$204.69	13.266%	$231.8442	$231.84	$231.85	$231.80
Purchase #4	$195.89	9.714%	$214.9188	$214.92	$214.90	$214.90
Purchase #5	$175.26	13.340%	$198.6397	$198.64	$198.65	$198.60
Purchase #6	$143.90	12.501%	$161.8889	$161.89	$161.90	$161.90
Purchase #7	$98.79	13.232%	$111.8619	$111.86	$111.85	$111.90
7 purchase totals =	$1,044.67		$1,167.0189	$1,167.01	$1,167.00	$1,167.00