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	$167.91	13.156%	$190.0002	$190.00	$190.00	$190.00
Purchase #2	$20.31	10.673%	$22.4777	$22.48	$22.50	$22.50
Purchase #3	$164.99	9.248%	$180.2483	$180.25	$180.25	$180.20
Purchase #4	$208.30	13.437%	$236.2893	$236.29	$236.30	$236.30
Purchase #5	$225.84	13.628%	$256.6175	$256.62	$256.60	$256.60
Purchase #6	$238.89	8.206%	$258.4933	$258.49	$258.50	$258.50
Purchase #7	$247.61	3.113%	$255.3181	$255.32	$255.30	$255.30
7 purchase totals =	$1,273.85		$1,399.4444	$1,399.45	$1,399.45	$1,399.40