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	$165.47	6.677%	$176.5184	$176.52	$176.50	$176.50
Purchase #2	$116.94	9.817%	$128.42	$128.42	$128.40	$128.40
Purchase #3	$33.45	13.700%	$38.0327	$38.03	$38.05	$38.00
Purchase #4	$88.92	13.533%	$100.9535	$100.95	$100.95	$101.00
Purchase #5	$49.90	13.234%	$56.5038	$56.50	$56.50	$56.50
Purchase #6	$218.26	5.175%	$229.555	$229.56	$229.55	$229.60
Purchase #7	$198.72	8.403%	$215.4184	$215.42	$215.40	$215.40
7 purchase totals =	$871.66		$945.4018	$945.40	$945.35	$945.40