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	$100.30	8.460%	$108.7854	$108.79	$108.80	$108.80
Purchase #2	$180.26	11.213%	$200.4726	$200.47	$200.45	$200.50
Purchase #3	$237.86	9.755%	$261.0632	$261.06	$261.05	$261.10
Purchase #4	$48.50	3.127%	$50.0166	$50.02	$50.00	$50.00
Purchase #5	$200.75	4.228%	$209.2377	$209.24	$209.25	$209.20
Purchase #6	$10.86	12.557%	$12.2237	$12.22	$12.20	$12.20
Purchase #7	$147.88	13.685%	$168.1174	$168.12	$168.10	$168.10
7 purchase totals =	$926.41		$1,009.9166	$1,009.92	$1,009.85	$1,009.90