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	$107.83	7.855%	$116.3	$116.30	$116.30	$116.30
Purchase #2	$52.64	4.293%	$54.8998	$54.90	$54.90	$54.90
Purchase #3	$105.86	4.479%	$110.6015	$110.60	$110.60	$110.60
Purchase #4	$183.30	7.383%	$196.833	$196.83	$196.85	$196.80
Purchase #5	$72.52	7.341%	$77.8437	$77.84	$77.85	$77.80
Purchase #6	$192.53	9.533%	$210.8839	$210.88	$210.90	$210.90
Purchase #7	$135.77	3.379%	$140.3577	$140.36	$140.35	$140.40
7 purchase totals =	$850.45		$907.7196	$907.71	$907.75	$907.70