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	$94.81	13.214%	$107.3382	$107.34	$107.35	$107.30
Purchase #2	$190.80	7.740%	$205.5679	$205.57	$205.55	$205.60
Purchase #3	$137.70	11.735%	$153.8591	$153.86	$153.85	$153.90
Purchase #4	$201.60	10.337%	$222.4394	$222.44	$222.45	$222.40
Purchase #5	$12.58	7.765%	$13.5568	$13.56	$13.55	$13.60
Purchase #6	$172.91	10.463%	$191.0016	$191.00	$191.00	$191.00
Purchase #7	$111.91	9.836%	$122.9175	$122.92	$122.90	$122.90
7 purchase totals =	$922.31		$1,016.6805	$1,016.69	$1,016.65	$1,016.70