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	$51.57	3.415%	$53.3311	$53.33	$53.35	$53.30
Purchase #2	$25.29	9.658%	$27.7325	$27.73	$27.75	$27.70
Purchase #3	$138.92	4.807%	$145.5979	$145.60	$145.60	$145.60
Purchase #4	$203.59	9.268%	$222.4587	$222.46	$222.45	$222.50
Purchase #5	$241.67	5.521%	$255.0126	$255.01	$255.00	$255.00
Purchase #6	$29.63	12.712%	$33.3966	$33.40	$33.40	$33.40
Purchase #7	$172.92	11.667%	$193.0946	$193.09	$193.10	$193.10
7 purchase totals =	$863.59		$930.6240	$930.62	$930.65	$930.60