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	$196.93	13.263%	$223.0488	$223.05	$223.05	$223.00
Purchase #2	$87.57	11.392%	$97.546	$97.55	$97.55	$97.50
Purchase #3	$99.68	11.462%	$111.1053	$111.11	$111.10	$111.10
Purchase #4	$36.81	4.873%	$38.6038	$38.60	$38.60	$38.60
Purchase #5	$94.72	3.189%	$97.7406	$97.74	$97.75	$97.70
Purchase #6	$196.86	8.526%	$213.6443	$213.64	$213.65	$213.60
Purchase #7	$55.50	11.548%	$61.9091	$61.91	$61.90	$61.90
7 purchase totals =	$768.07		$843.5979	$843.60	$843.60	$843.40