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	$217.27	11.597%	$242.4668	$242.47	$242.45	$242.50
Purchase #2	$108.71	13.247%	$123.1108	$123.11	$123.10	$123.10
Purchase #3	$89.60	5.315%	$94.3622	$94.36	$94.35	$94.40
Purchase #4	$84.78	5.757%	$89.6608	$89.66	$89.65	$89.70
Purchase #5	$49.29	3.320%	$50.9264	$50.93	$50.95	$50.90
Purchase #6	$59.66	11.414%	$66.4696	$66.47	$66.45	$66.50
Purchase #7	$193.90	8.582%	$210.5405	$210.54	$210.55	$210.50
7 purchase totals =	$803.21		$877.5371	$877.54	$877.50	$877.60