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	$221.89	8.852%	$241.5317	$241.53	$241.55	$241.50
Purchase #2	$113.72	8.599%	$123.4988	$123.50	$123.50	$123.50
Purchase #3	$241.52	6.712%	$257.7308	$257.73	$257.75	$257.70
Purchase #4	$215.50	4.821%	$225.8893	$225.89	$225.90	$225.90
Purchase #5	$84.53	7.352%	$90.7446	$90.74	$90.75	$90.70
Purchase #6	$58.64	13.615%	$66.6238	$66.62	$66.60	$66.60
Purchase #7	$195.33	6.339%	$207.712	$207.71	$207.70	$207.70
7 purchase totals =	$1,131.13		$1,213.7310	$1,213.72	$1,213.75	$1,213.60