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	$187.79	6.660%	$200.2968	$200.30	$200.30	$200.30
Purchase #2	$80.78	12.236%	$90.6642	$90.66	$90.65	$90.70
Purchase #3	$205.40	9.358%	$224.6213	$224.62	$224.60	$224.60
Purchase #4	$28.93	4.764%	$30.3082	$30.31	$30.30	$30.30
Purchase #5	$146.86	12.659%	$165.451	$165.45	$165.45	$165.50
Purchase #6	$127.71	11.867%	$142.8653	$142.87	$142.85	$142.90
Purchase #7	$206.49	4.569%	$215.9245	$215.92	$215.90	$215.90
7 purchase totals =	$983.96		$1,070.1313	$1,070.13	$1,070.05	$1,070.20