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	$134.98	3.670%	$139.9338	$139.93	$139.95	$139.90
Purchase #2	$218.39	10.843%	$242.07	$242.07	$242.05	$242.10
Purchase #3	$20.93	9.184%	$22.8522	$22.85	$22.85	$22.90
Purchase #4	$5.97	12.532%	$6.7182	$6.72	$6.70	$6.70
Purchase #5	$81.83	10.464%	$90.3927	$90.39	$90.40	$90.40
Purchase #6	$60.47	10.564%	$66.8581	$66.86	$66.85	$66.90
Purchase #7	$163.60	5.405%	$172.4426	$172.44	$172.45	$172.40
7 purchase totals =	$686.17		$741.2676	$741.26	$741.25	$741.30