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	$103.69	13.817%	$118.0168	$118.02	$118.00	$118.00
Purchase #2	$243.60	5.202%	$256.2721	$256.27	$256.25	$256.30
Purchase #3	$95.29	5.274%	$100.3156	$100.32	$100.30	$100.30
Purchase #4	$140.76	10.867%	$156.0564	$156.06	$156.05	$156.10
Purchase #5	$129.53	5.172%	$136.2293	$136.23	$136.25	$136.20
Purchase #6	$237.43	12.276%	$266.5769	$266.58	$266.60	$266.60
Purchase #7	$126.57	9.797%	$138.9701	$138.97	$138.95	$139.00
7 purchase totals =	$1,076.87		$1,172.4372	$1,172.45	$1,172.40	$1,172.50