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	$121.25	13.845%	$138.0371	$138.04	$138.05	$138.00
Purchase #2	$133.40	6.837%	$142.5206	$142.52	$142.50	$142.50
Purchase #3	$203.77	11.635%	$227.4786	$227.48	$227.50	$227.50
Purchase #4	$132.82	13.107%	$150.2287	$150.23	$150.25	$150.20
Purchase #5	$84.76	9.179%	$92.5401	$92.54	$92.55	$92.50
Purchase #6	$146.39	9.828%	$160.7772	$160.78	$160.80	$160.80
Purchase #7	$96.96	8.220%	$104.9301	$104.93	$104.95	$104.90
7 purchase totals =	$919.35		$1,016.5124	$1,016.52	$1,016.60	$1,016.40