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	$204.59	13.610%	$232.4347	$232.43	$232.45	$232.40
Purchase #2	$50.69	3.783%	$52.6076	$52.61	$52.60	$52.60
Purchase #3	$179.53	11.361%	$199.9264	$199.93	$199.95	$199.90
Purchase #4	$126.57	10.873%	$140.332	$140.33	$140.35	$140.30
Purchase #5	$83.99	10.610%	$92.9013	$92.90	$92.90	$92.90
Purchase #6	$134.45	13.371%	$152.4273	$152.43	$152.45	$152.40
Purchase #7	$233.95	3.128%	$241.268	$241.27	$241.25	$241.30
7 purchase totals =	$1,013.77		$1,111.8973	$1,111.90	$1,111.95	$1,111.80