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	$173.67	12.714%	$195.7504	$195.75	$195.75	$195.80
Purchase #2	$178.26	11.543%	$198.8366	$198.84	$198.85	$198.80
Purchase #3	$80.78	3.551%	$83.6485	$83.65	$83.65	$83.60
Purchase #4	$95.89	4.813%	$100.5052	$100.51	$100.50	$100.50
Purchase #5	$100.35	12.870%	$113.265	$113.27	$113.25	$113.30
Purchase #6	$129.98	11.783%	$145.2955	$145.30	$145.30	$145.30
Purchase #7	$11.40	9.767%	$12.5134	$12.51	$12.50	$12.50
7 purchase totals =	$770.33		$849.8146	$849.83	$849.80	$849.80