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	$65.83	6.147%	$69.8766	$69.88	$69.90	$69.90
Purchase #2	$182.40	4.657%	$190.8944	$190.89	$190.90	$190.90
Purchase #3	$56.78	4.718%	$59.4589	$59.46	$59.45	$59.50
Purchase #4	$100.85	6.715%	$107.6221	$107.62	$107.60	$107.60
Purchase #5	$190.40	10.131%	$209.6894	$209.69	$209.70	$209.70
Purchase #6	$200.99	3.132%	$207.285	$207.29	$207.30	$207.30
Purchase #7	$56.46	10.775%	$62.5436	$62.54	$62.55	$62.50
7 purchase totals =	$853.71		$907.3700	$907.37	$907.40	$907.40