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	$99.94	11.862%	$111.7949	$111.79	$111.80	$111.80
Purchase #2	$51.87	7.703%	$55.8655	$55.87	$55.85	$55.90
Purchase #3	$41.64	3.147%	$42.9504	$42.95	$42.95	$43.00
Purchase #4	$113.34	12.165%	$127.1278	$127.13	$127.15	$127.10
Purchase #5	$63.89	10.704%	$70.7288	$70.73	$70.75	$70.70
Purchase #6	$136.86	12.571%	$154.0647	$154.06	$154.05	$154.10
Purchase #7	$43.72	4.769%	$45.805	$45.81	$45.80	$45.80
7 purchase totals =	$551.26		$608.3371	$608.34	$608.35	$608.40