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	$239.67	6.284%	$254.7309	$254.73	$254.75	$254.70
Purchase #2	$237.91	7.536%	$255.8389	$255.84	$255.85	$255.80
Purchase #3	$162.35	5.688%	$171.5845	$171.58	$171.60	$171.60
Purchase #4	$26.32	6.733%	$28.0921	$28.09	$28.10	$28.10
Purchase #5	$13.71	6.160%	$14.5545	$14.55	$14.55	$14.60
Purchase #6	$42.97	5.402%	$45.2912	$45.29	$45.30	$45.30
Purchase #7	$98.53	13.219%	$111.5547	$111.55	$111.55	$111.60
7 purchase totals =	$821.46		$881.6468	$881.63	$881.70	$881.70