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	$143.29	12.422%	$161.0895	$161.09	$161.10	$161.10
Purchase #2	$66.76	7.816%	$71.978	$71.98	$72.00	$72.00
Purchase #3	$81.94	10.337%	$90.4101	$90.41	$90.40	$90.40
Purchase #4	$94.38	10.498%	$104.288	$104.29	$104.30	$104.30
Purchase #5	$68.41	11.746%	$76.4454	$76.45	$76.45	$76.40
Purchase #6	$218.58	9.209%	$238.709	$238.71	$238.70	$238.70
Purchase #7	$224.27	8.224%	$242.714	$242.71	$242.70	$242.70
7 purchase totals =	$897.63		$985.6340	$985.64	$985.65	$985.60