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	$173.34	3.112%	$178.7343	$178.73	$178.75	$178.70
Purchase #2	$28.63	3.122%	$29.5238	$29.52	$29.50	$29.50
Purchase #3	$28.72	8.123%	$31.0529	$31.05	$31.05	$31.10
Purchase #4	$38.43	9.382%	$42.0355	$42.04	$42.05	$42.00
Purchase #5	$84.42	3.702%	$87.5452	$87.55	$87.55	$87.50
Purchase #6	$102.39	4.516%	$107.0139	$107.01	$107.00	$107.00
Purchase #7	$172.87	10.243%	$190.5771	$190.58	$190.60	$190.60
7 purchase totals =	$628.80		$666.4827	$666.48	$666.50	$666.40