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	$116.63	10.362%	$128.7152	$128.72	$128.70	$128.70
Purchase #2	$152.56	12.589%	$171.7658	$171.77	$171.75	$171.80
Purchase #3	$86.32	9.789%	$94.7699	$94.77	$94.75	$94.80
Purchase #4	$233.46	3.284%	$241.1268	$241.13	$241.15	$241.10
Purchase #5	$189.96	3.410%	$196.4376	$196.44	$196.45	$196.40
Purchase #6	$75.30	10.397%	$83.1289	$83.13	$83.15	$83.10
Purchase #7	$92.87	8.244%	$100.5262	$100.53	$100.55	$100.50
7 purchase totals =	$947.10		$1,016.4704	$1,016.49	$1,016.50	$1,016.40