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	$94.65	13.579%	$107.5025	$107.50	$107.50	$107.50
Purchase #2	$215.31	3.709%	$223.2958	$223.30	$223.30	$223.30
Purchase #3	$99.25	6.132%	$105.336	$105.34	$105.35	$105.30
Purchase #4	$96.58	3.864%	$100.3119	$100.31	$100.30	$100.30
Purchase #5	$66.81	9.767%	$73.3353	$73.34	$73.35	$73.30
Purchase #6	$20.37	4.786%	$21.3449	$21.34	$21.35	$21.30
Purchase #7	$98.46	13.208%	$111.4646	$111.46	$111.45	$111.50
7 purchase totals =	$691.43		$742.5910	$742.59	$742.60	$742.50