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	$238.61	11.534%	$266.1313	$266.13	$266.15	$266.10
Purchase #2	$144.91	4.772%	$151.8251	$151.83	$151.85	$151.80
Purchase #3	$111.60	6.354%	$118.6911	$118.69	$118.70	$118.70
Purchase #4	$240.55	10.351%	$265.4493	$265.45	$265.45	$265.40
Purchase #5	$80.90	11.864%	$90.498	$90.50	$90.50	$90.50
Purchase #6	$74.62	4.714%	$78.1376	$78.14	$78.15	$78.10
Purchase #7	$35.28	4.533%	$36.8792	$36.88	$36.90	$36.90
7 purchase totals =	$926.47		$1,007.6116	$1,007.62	$1,007.70	$1,007.50