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	$102.76	4.686%	$107.5753	$107.58	$107.60	$107.60
Purchase #2	$169.53	5.203%	$178.3506	$178.35	$178.35	$178.40
Purchase #3	$38.72	12.350%	$43.5019	$43.50	$43.50	$43.50
Purchase #4	$196.77	13.524%	$223.3812	$223.38	$223.40	$223.40
Purchase #5	$189.75	3.518%	$196.4254	$196.43	$196.45	$196.40
Purchase #6	$188.72	7.276%	$202.4513	$202.45	$202.45	$202.50
Purchase #7	$199.72	9.749%	$219.1907	$219.19	$219.20	$219.20
7 purchase totals =	$1,085.97		$1,170.8764	$1,170.88	$1,170.95	$1,171.00