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	$137.33	9.706%	$150.6592	$150.66	$150.65	$150.70
Purchase #2	$90.60	9.420%	$99.1345	$99.13	$99.15	$99.10
Purchase #3	$73.72	9.714%	$80.8812	$80.88	$80.90	$80.90
Purchase #4	$21.74	10.296%	$23.9784	$23.98	$24.00	$24.00
Purchase #5	$97.61	12.537%	$109.8474	$109.85	$109.85	$109.80
Purchase #6	$137.82	12.435%	$154.9579	$154.96	$154.95	$155.00
Purchase #7	$102.77	10.408%	$113.4663	$113.47	$113.45	$113.50
7 purchase totals =	$661.59		$732.9249	$732.93	$732.95	$733.00