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	$140.76	5.349%	$148.2893	$148.29	$148.30	$148.30
Purchase #2	$229.66	10.858%	$254.5965	$254.60	$254.60	$254.60
Purchase #3	$99.98	4.342%	$104.3211	$104.32	$104.30	$104.30
Purchase #4	$19.40	10.655%	$21.4671	$21.47	$21.45	$21.50
Purchase #5	$53.87	7.770%	$58.0557	$58.06	$58.05	$58.10
Purchase #6	$95.50	3.185%	$98.5417	$98.54	$98.55	$98.50
Purchase #7	$41.79	13.735%	$47.5299	$47.53	$47.55	$47.50
7 purchase totals =	$680.96		$732.8013	$732.81	$732.80	$732.80