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	$32.55	9.467%	$35.6315	$35.63	$35.65	$35.60
Purchase #2	$233.42	12.603%	$262.8379	$262.84	$262.85	$262.80
Purchase #3	$190.75	6.786%	$203.6943	$203.69	$203.70	$203.70
Purchase #4	$87.92	5.131%	$92.4312	$92.43	$92.45	$92.40
Purchase #5	$123.80	8.545%	$134.3787	$134.38	$134.40	$134.40
Purchase #6	$164.56	13.588%	$186.9204	$186.92	$186.90	$186.90
Purchase #7	$80.77	7.171%	$86.562	$86.56	$86.55	$86.60
7 purchase totals =	$913.77		$1,002.4560	$1,002.45	$1,002.50	$1,002.40