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	$120.33	11.109%	$133.6975	$133.70	$133.70	$133.70
Purchase #2	$179.42	10.858%	$198.9014	$198.90	$198.90	$198.90
Purchase #3	$205.51	13.640%	$233.5416	$233.54	$233.55	$233.50
Purchase #4	$13.69	8.738%	$14.8862	$14.89	$14.90	$14.90
Purchase #5	$106.37	6.497%	$113.2809	$113.28	$113.30	$113.30
Purchase #6	$182.92	5.311%	$192.6349	$192.63	$192.65	$192.60
Purchase #7	$116.94	9.828%	$128.4329	$128.43	$128.45	$128.40
7 purchase totals =	$925.18		$1,015.3754	$1,015.37	$1,015.45	$1,015.30