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	$164.45	9.213%	$179.6008	$179.60	$179.60	$179.60
Purchase #2	$225.30	12.779%	$254.0911	$254.09	$254.10	$254.10
Purchase #3	$160.34	8.835%	$174.506	$174.51	$174.50	$174.50
Purchase #4	$136.45	6.145%	$144.8349	$144.83	$144.85	$144.80
Purchase #5	$98.55	4.299%	$102.7867	$102.79	$102.80	$102.80
Purchase #6	$168.86	5.140%	$177.5394	$177.54	$177.55	$177.50
Purchase #7	$146.73	7.762%	$158.1192	$158.12	$158.10	$158.10
7 purchase totals =	$1,100.68		$1,191.4781	$1,191.48	$1,191.50	$1,191.40