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	$117.55	9.367%	$128.5609	$128.56	$128.55	$128.60
Purchase #2	$128.38	10.245%	$141.5325	$141.53	$141.55	$141.50
Purchase #3	$231.58	6.693%	$247.0796	$247.08	$247.10	$247.10
Purchase #4	$38.82	9.104%	$42.3542	$42.35	$42.35	$42.40
Purchase #5	$250.86	13.851%	$285.6066	$285.61	$285.60	$285.60
Purchase #6	$109.68	6.302%	$116.592	$116.59	$116.60	$116.60
Purchase #7	$61.77	10.228%	$68.0878	$68.09	$68.10	$68.10
7 purchase totals =	$938.64		$1,029.8136	$1,029.81	$1,029.85	$1,029.90