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	$103.86	8.134%	$112.308	$112.31	$112.30	$112.30
Purchase #2	$112.51	7.121%	$120.5218	$120.52	$120.50	$120.50
Purchase #3	$112.96	11.681%	$126.1549	$126.15	$126.15	$126.20
Purchase #4	$198.52	12.226%	$222.7911	$222.79	$222.80	$222.80
Purchase #5	$64.71	12.775%	$72.9767	$72.98	$73.00	$73.00
Purchase #6	$46.95	9.565%	$51.4408	$51.44	$51.45	$51.40
Purchase #7	$241.26	5.748%	$255.1276	$255.13	$255.15	$255.10
7 purchase totals =	$880.77		$961.3209	$961.32	$961.35	$961.30