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	$165.28	9.441%	$180.8841	$180.88	$180.90	$180.90
Purchase #2	$18.59	10.746%	$20.5877	$20.59	$20.60	$20.60
Purchase #3	$156.79	10.295%	$172.9315	$172.93	$172.95	$172.90
Purchase #4	$52.43	8.684%	$56.983	$56.98	$57.00	$57.00
Purchase #5	$142.84	7.517%	$153.5773	$153.58	$153.60	$153.60
Purchase #6	$223.38	3.660%	$231.5557	$231.56	$231.55	$231.60
Purchase #7	$238.41	13.608%	$270.8528	$270.85	$270.85	$270.90
7 purchase totals =	$997.72		$1,087.3721	$1,087.37	$1,087.45	$1,087.50