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	$14.94	10.465%	$16.5035	$16.50	$16.50	$16.50
Purchase #2	$215.63	13.612%	$244.9816	$244.98	$245.00	$245.00
Purchase #3	$80.74	11.801%	$90.2681	$90.27	$90.25	$90.30
Purchase #4	$113.72	12.405%	$127.827	$127.83	$127.85	$127.80
Purchase #5	$170.27	6.789%	$181.8296	$181.83	$181.85	$181.80
Purchase #6	$22.49	3.583%	$23.2958	$23.30	$23.30	$23.30
Purchase #7	$8.81	13.854%	$10.0305	$10.03	$10.05	$10.00
7 purchase totals =	$626.60		$694.7361	$694.74	$694.80	$694.70