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	$93.52	11.794%	$104.5497	$104.55	$104.55	$104.50
Purchase #2	$235.84	10.702%	$261.0796	$261.08	$261.10	$261.10
Purchase #3	$99.65	11.422%	$111.032	$111.03	$111.05	$111.00
Purchase #4	$210.38	13.564%	$238.9159	$238.92	$238.90	$238.90
Purchase #5	$113.67	11.116%	$126.3056	$126.31	$126.30	$126.30
Purchase #6	$156.96	7.674%	$169.0051	$169.01	$169.00	$169.00
Purchase #7	$149.79	7.873%	$161.583	$161.58	$161.60	$161.60
7 purchase totals =	$1,059.81		$1,172.4709	$1,172.48	$1,172.50	$1,172.40