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	$99.92	11.107%	$111.0181	$111.02	$111.00	$111.00
Purchase #2	$210.35	6.264%	$223.5263	$223.53	$223.55	$223.50
Purchase #3	$226.67	5.577%	$239.3114	$239.31	$239.30	$239.30
Purchase #4	$217.77	9.519%	$238.4995	$238.50	$238.50	$238.50
Purchase #5	$165.70	4.460%	$173.0902	$173.09	$173.10	$173.10
Purchase #6	$188.36	11.869%	$210.7164	$210.72	$210.70	$210.70
Purchase #7	$25.35	8.216%	$27.4328	$27.43	$27.45	$27.40
7 purchase totals =	$1,134.12		$1,223.5947	$1,223.60	$1,223.60	$1,223.50