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	$131.55	9.770%	$144.4024	$144.40	$144.40	$144.40
Purchase #2	$98.58	3.721%	$102.2482	$102.25	$102.25	$102.20
Purchase #3	$51.27	5.810%	$54.2488	$54.25	$54.25	$54.20
Purchase #4	$45.82	4.405%	$47.8384	$47.84	$47.85	$47.80
Purchase #5	$189.47	9.524%	$207.5151	$207.52	$207.50	$207.50
Purchase #6	$86.63	4.851%	$90.8324	$90.83	$90.85	$90.80
Purchase #7	$220.49	8.187%	$238.5415	$238.54	$238.55	$238.50
7 purchase totals =	$823.81		$885.6268	$885.63	$885.65	$885.40