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	$217.97	11.178%	$242.3347	$242.33	$242.35	$242.30
Purchase #2	$68.30	5.126%	$71.8011	$71.80	$71.80	$71.80
Purchase #3	$64.80	4.171%	$67.5028	$67.50	$67.50	$67.50
Purchase #4	$65.46	3.407%	$67.6902	$67.69	$67.70	$67.70
Purchase #5	$73.78	6.466%	$78.5506	$78.55	$78.55	$78.60
Purchase #6	$196.46	9.231%	$214.5952	$214.60	$214.60	$214.60
Purchase #7	$68.60	4.396%	$71.6157	$71.62	$71.60	$71.60
7 purchase totals =	$755.37		$814.0903	$814.09	$814.10	$814.10