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	$218.44	9.616%	$239.4452	$239.45	$239.45	$239.40
Purchase #2	$40.39	7.545%	$43.4374	$43.44	$43.45	$43.40
Purchase #3	$155.75	12.682%	$175.5022	$175.50	$175.50	$175.50
Purchase #4	$173.58	3.573%	$179.782	$179.78	$179.80	$179.80
Purchase #5	$39.37	9.263%	$43.0168	$43.02	$43.00	$43.00
Purchase #6	$170.41	13.336%	$193.1359	$193.14	$193.15	$193.10
Purchase #7	$57.37	3.606%	$59.4388	$59.44	$59.45	$59.40
7 purchase totals =	$855.31		$933.7583	$933.77	$933.80	$933.60