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	$120.77	7.866%	$130.2698	$130.27	$130.25	$130.30
Purchase #2	$92.92	13.346%	$105.3211	$105.32	$105.30	$105.30
Purchase #3	$221.98	5.379%	$233.9203	$233.92	$233.90	$233.90
Purchase #4	$124.63	13.827%	$141.8626	$141.86	$141.85	$141.90
Purchase #5	$96.81	10.816%	$107.281	$107.28	$107.30	$107.30
Purchase #6	$217.88	4.385%	$227.434	$227.43	$227.45	$227.40
Purchase #7	$168.59	5.314%	$177.5489	$177.55	$177.55	$177.50
7 purchase totals =	$1,043.58		$1,123.6377	$1,123.63	$1,123.60	$1,123.60