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	$192.27	11.828%	$215.0117	$215.01	$215.00	$215.00
Purchase #2	$113.35	6.363%	$120.5625	$120.56	$120.55	$120.60
Purchase #3	$91.68	3.429%	$94.8237	$94.82	$94.80	$94.80
Purchase #4	$62.41	8.314%	$67.5988	$67.60	$67.60	$67.60
Purchase #5	$168.47	6.773%	$179.8805	$179.88	$179.90	$179.90
Purchase #6	$219.34	3.773%	$227.6157	$227.62	$227.60	$227.60
Purchase #7	$5.83	5.476%	$6.1493	$6.15	$6.15	$6.10
7 purchase totals =	$853.35		$911.6422	$911.64	$911.60	$911.60