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	$169.45	6.276%	$180.0847	$180.08	$180.10	$180.10
Purchase #2	$77.73	3.798%	$80.6822	$80.68	$80.70	$80.70
Purchase #3	$181.30	8.241%	$196.2409	$196.24	$196.25	$196.20
Purchase #4	$168.42	7.161%	$180.4806	$180.48	$180.50	$180.50
Purchase #5	$99.91	4.437%	$104.343	$104.34	$104.35	$104.30
Purchase #6	$143.85	9.861%	$158.035	$158.04	$158.05	$158.00
Purchase #7	$155.87	5.465%	$164.3883	$164.39	$164.40	$164.40
7 purchase totals =	$996.53		$1,064.2547	$1,064.25	$1,064.35	$1,064.20