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	$102.92	13.129%	$116.4324	$116.43	$116.45	$116.40
Purchase #2	$172.85	6.676%	$184.3895	$184.39	$184.40	$184.40
Purchase #3	$46.28	4.194%	$48.221	$48.22	$48.20	$48.20
Purchase #4	$112.38	13.292%	$127.3175	$127.32	$127.30	$127.30
Purchase #5	$73.77	6.383%	$78.4787	$78.48	$78.50	$78.50
Purchase #6	$157.26	5.786%	$166.3591	$166.36	$166.35	$166.40
Purchase #7	$238.82	6.362%	$254.0137	$254.01	$254.00	$254.00
7 purchase totals =	$904.28		$975.2119	$975.21	$975.20	$975.20