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	$202.54	13.291%	$229.4596	$229.46	$229.45	$229.50
Purchase #2	$116.81	12.702%	$131.6472	$131.65	$131.65	$131.60
Purchase #3	$148.35	10.730%	$164.268	$164.27	$164.25	$164.30
Purchase #4	$236.75	13.414%	$268.5076	$268.51	$268.50	$268.50
Purchase #5	$70.87	9.320%	$77.4751	$77.48	$77.50	$77.50
Purchase #6	$105.59	11.657%	$117.8986	$117.90	$117.90	$117.90
Purchase #7	$132.45	3.774%	$137.4487	$137.45	$137.45	$137.40
7 purchase totals =	$1,013.36		$1,126.7048	$1,126.72	$1,126.70	$1,126.70