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	$92.94	12.336%	$104.4051	$104.41	$104.40	$104.40
Purchase #2	$127.53	13.349%	$144.554	$144.55	$144.55	$144.60
Purchase #3	$40.78	4.834%	$42.7513	$42.75	$42.75	$42.80
Purchase #4	$60.29	5.198%	$63.4239	$63.42	$63.40	$63.40
Purchase #5	$170.60	3.453%	$176.4908	$176.49	$176.50	$176.50
Purchase #6	$89.49	3.755%	$92.8503	$92.85	$92.85	$92.90
Purchase #7	$81.50	7.780%	$87.8407	$87.84	$87.85	$87.80
7 purchase totals =	$663.13		$712.3161	$712.31	$712.30	$712.40